diff --git a/headers/enduro2d/high/_all.hpp b/headers/enduro2d/high/_all.hpp
index bae45e74..c606f84f 100644
--- a/headers/enduro2d/high/_all.hpp
+++ b/headers/enduro2d/high/_all.hpp
@@ -30,6 +30,9 @@
 
 #include "systems/render_system.hpp"
 
+#include "address.hpp"
+#include "asset.hpp"
+#include "asset.inl"
 #include "atlas.hpp"
 #include "flipbook.hpp"
 #include "library.hpp"
diff --git a/headers/enduro2d/high/_high.hpp b/headers/enduro2d/high/_high.hpp
index b87bfda1..fe744a79 100644
--- a/headers/enduro2d/high/_high.hpp
+++ b/headers/enduro2d/high/_high.hpp
@@ -44,14 +44,14 @@ namespace e2d
 
     template < typename Asset, typename Content >
     class content_asset;
-    class content_asset_base;
-
-    class library;
+    class asset;
 
     template < typename T >
     class asset_cache;
     class asset_cache_base;
 
+    class library;
+
     class atlas;
     class flipbook;
     class model;
diff --git a/headers/enduro2d/high/address.hpp b/headers/enduro2d/high/address.hpp
new file mode 100644
index 00000000..46a00ba6
--- /dev/null
+++ b/headers/enduro2d/high/address.hpp
@@ -0,0 +1,15 @@
+/*******************************************************************************
+ * This file is part of the "Enduro2D"
+ * For conditions of distribution and use, see copyright notice in LICENSE.md
+ * Copyright (C) 2018-2019 Matvey Cherevko
+ ******************************************************************************/
+
+#pragma once
+
+#include "_high.hpp"
+
+namespace e2d { namespace address
+{
+    str parent(str_view address);
+    str nested(str_view address);
+}}
diff --git a/headers/enduro2d/high/asset.hpp b/headers/enduro2d/high/asset.hpp
new file mode 100644
index 00000000..39ffd6ca
--- /dev/null
+++ b/headers/enduro2d/high/asset.hpp
@@ -0,0 +1,148 @@
+/*******************************************************************************
+ * This file is part of the "Enduro2D"
+ * For conditions of distribution and use, see copyright notice in LICENSE.md
+ * Copyright (C) 2018-2019 Matvey Cherevko
+ ******************************************************************************/
+
+#ifndef E2D_INCLUDE_GUARD_1122A7CA62954AEF9E0A787064D28F73
+#define E2D_INCLUDE_GUARD_1122A7CA62954AEF9E0A787064D28F73
+#pragma once
+
+#include "_high.hpp"
+
+namespace e2d
+{
+    //
+    // asset_loading_exception
+    //
+
+    class asset_loading_exception : public exception {
+        const char* what() const noexcept override {
+            return "asset loading exception";
+        }
+    };
+
+    //
+    // bad_asset_factory_operation
+    //
+
+    class bad_asset_factory_operation final : public exception {
+    public:
+        const char* what() const noexcept final {
+            return "bad asset factory operation";
+        }
+    };
+
+    //
+    // asset
+    //
+
+    class asset;
+    using asset_ptr = intrusive_ptr<asset>;
+    using nested_content = hash_map<str_hash, asset_ptr>;
+
+    class asset
+        : private noncopyable
+        , public ref_counter<asset> {
+    public:
+        asset();
+        virtual ~asset() noexcept;
+        virtual asset_ptr find_nested_asset(str_view name) const noexcept = 0;
+    };
+
+    //
+    // content_asset
+    //
+
+    template < typename Asset, typename Content >
+    class content_asset : public asset {
+    public:
+        using asset_type = Asset;
+        using content_type = Content;
+
+        using ptr = intrusive_ptr<Asset>;
+        using load_result = intrusive_ptr<Asset>;
+        using load_async_result = stdex::promise<load_result>;
+    public:
+        static load_result create();
+        static load_result create(Content content);
+        static load_result create(Content content, nested_content nested_content);
+
+        void fill(Content content);
+        void fill(Content content, nested_content nested_content);
+
+        const Content& content() const noexcept;
+
+        template < typename T >
+        intrusive_ptr<T> find_nested_asset(str_view name) const noexcept;
+        asset_ptr find_nested_asset(str_view name) const noexcept override;
+    private:
+        Content content_;
+        nested_content nested_content_;
+    };
+
+    //
+    // asset_cache_base
+    //
+
+    class asset_cache_base : private noncopyable {
+    public:
+        asset_cache_base();
+        virtual ~asset_cache_base() noexcept;
+
+        static std::size_t unload_all_unused_assets() noexcept;
+        virtual std::size_t unload_self_unused_assets() noexcept = 0;
+    private:
+        static std::mutex mutex_;
+        static hash_set<asset_cache_base*> caches_;
+    };
+
+    //
+    // asset_cache
+    //
+
+    template < typename Asset >
+    class asset_cache : public asset_cache_base
+                      , public module<asset_cache<Asset>> {
+    public:
+        using asset_ptr = typename Asset::ptr;
+    public:
+        asset_cache(library& l);
+        ~asset_cache() noexcept final;
+
+        asset_ptr find(str_hash address) const noexcept;
+        void store(str_hash address, const asset_ptr& asset);
+
+        void clear() noexcept;
+        std::size_t asset_count() const noexcept;
+
+        std::size_t unload_self_unused_assets() noexcept override;
+    private:
+        library& library_;
+        mutable std::mutex mutex_;
+        hash_map<str_hash, asset_ptr> assets_;
+    };
+
+    //
+    // asset_factory
+    //
+
+    class asset_factory : public module<asset_factory> {
+    public:
+        using asset_creator = std::function<
+            stdex::promise<asset_ptr>(const library& library, str_view address)>;
+    public:
+        asset_factory();
+        ~asset_factory() noexcept final;
+
+        template < typename Asset >
+        asset_factory& register_asset(str_hash type);
+        asset_factory& register_creator(str_hash type, asset_creator creator);
+    private:
+        std::mutex mutex_;
+        hash_map<str_hash, asset_creator> creators_;
+    };
+}
+
+#include "asset.inl"
+#endif
diff --git a/headers/enduro2d/high/asset.inl b/headers/enduro2d/high/asset.inl
new file mode 100644
index 00000000..801e0b08
--- /dev/null
+++ b/headers/enduro2d/high/asset.inl
@@ -0,0 +1,150 @@
+/*******************************************************************************
+ * This file is part of the "Enduro2D"
+ * For conditions of distribution and use, see copyright notice in LICENSE.md
+ * Copyright (C) 2018-2019 Matvey Cherevko
+ ******************************************************************************/
+
+#ifndef E2D_INCLUDE_GUARD_6FD0B1DD12004CF78E7AC5FBBC36E854
+#define E2D_INCLUDE_GUARD_6FD0B1DD12004CF78E7AC5FBBC36E854
+#pragma once
+
+#include "_high.hpp"
+#include "asset.hpp"
+
+namespace e2d
+{
+    //
+    // content_asset
+    //
+
+    template < typename Asset, typename Content >
+    typename content_asset<Asset, Content>::load_result
+    content_asset<Asset, Content>::create() {
+        return load_result(new Asset());
+    }
+
+    template < typename Asset, typename Content >
+    typename content_asset<Asset, Content>::load_result
+    content_asset<Asset, Content>::create(Content content) {
+        auto result = create();
+        result->fill(std::move(content));
+        return result;
+    }
+
+    template < typename Asset, typename Content >
+    typename content_asset<Asset, Content>::load_result
+    content_asset<Asset, Content>::create(Content content, nested_content nested_content) {
+        auto result = create();
+        result->fill(std::move(content), std::move(nested_content));
+        return result;
+    }
+
+    template < typename Asset, typename Content >
+    void content_asset<Asset, Content>::fill(Content content) {
+        content_ = std::move(content);
+    }
+
+    template < typename Asset, typename Content >
+    void content_asset<Asset, Content>::fill(Content content, nested_content nested_content) {
+        content_ = std::move(content);
+        nested_content_ = std::move(nested_content);
+    }
+
+    template < typename Asset, typename Content >
+    const Content& content_asset<Asset, Content>::content() const noexcept {
+        return content_;
+    }
+
+    template < typename Asset, typename Content >
+    template < typename T >
+    intrusive_ptr<T> content_asset<Asset, Content>::find_nested_asset(str_view name) const noexcept {
+        return dynamic_pointer_cast<T>(find_nested_asset(name));
+    }
+
+    template < typename Asset, typename Content >
+    asset_ptr content_asset<Asset, Content>::find_nested_asset(str_view name) const noexcept {
+        const auto iter = nested_content_.find(name);
+        return iter != nested_content_.end()
+            ? iter->second
+            : nullptr;
+    }
+
+    //
+    // asset_cache
+    //
+
+    template < typename T >
+    asset_cache<T>::asset_cache(library& l)
+    : library_(l) {}
+
+    template < typename T >
+    asset_cache<T>::~asset_cache() noexcept = default;
+
+    template < typename T >
+    typename asset_cache<T>::asset_ptr asset_cache<T>::find(str_hash address) const noexcept {
+        std::lock_guard<std::mutex> guard(mutex_);
+        const auto iter = assets_.find(address);
+        return iter != assets_.end()
+            ? iter->second
+            : nullptr;
+    }
+
+    template < typename T >
+    void asset_cache<T>::store(str_hash address, const asset_ptr& asset) {
+        std::lock_guard<std::mutex> guard(mutex_);
+        assets_[address] = asset;
+    }
+
+    template < typename T >
+    void asset_cache<T>::clear() noexcept {
+        std::lock_guard<std::mutex> guard(mutex_);
+        assets_.clear();
+    }
+
+    template < typename T >
+    std::size_t asset_cache<T>::asset_count() const noexcept {
+        std::lock_guard<std::mutex> guard(mutex_);
+        return assets_.size();
+    }
+
+    template < typename T >
+    std::size_t asset_cache<T>::unload_self_unused_assets() noexcept {
+        std::lock_guard<std::mutex> guard(mutex_);
+        std::size_t result = 0u;
+        for ( auto iter = assets_.begin(); iter != assets_.end(); ) {
+            if ( !iter->second || 1 == iter->second->use_count() ) {
+                iter = assets_.erase(iter);
+                ++result;
+            } else {
+                ++iter;
+            }
+        }
+        return result;
+    }
+
+    //
+    // asset_factory
+    //
+
+    template < typename Asset >
+    asset_factory& asset_factory::register_asset(str_hash type) {
+        return register_creator(type, [](const library& library, str_view address) {
+            return Asset::load_async(library, address)
+                .then([](const typename Asset::load_result& result){
+                    return static_pointer_cast<asset>(result);
+                });
+        });
+    }
+
+    inline asset_factory& asset_factory::register_creator(str_hash type, asset_creator creator) {
+        std::lock_guard<std::mutex> guard(mutex_);
+        bool success = creators_.insert(
+            std::make_pair(type, std::move(creator))).second;
+        if ( !success ) {
+            throw bad_asset_factory_operation();
+        }
+        return *this;
+    }
+}
+
+#endif
diff --git a/headers/enduro2d/high/assets/atlas_asset.hpp b/headers/enduro2d/high/assets/atlas_asset.hpp
index c333d181..38b268df 100644
--- a/headers/enduro2d/high/assets/atlas_asset.hpp
+++ b/headers/enduro2d/high/assets/atlas_asset.hpp
@@ -8,15 +8,13 @@
 
 #include "../_high.hpp"
 
-#include "../atlas.hpp"
 #include "../library.hpp"
+#include "../atlas.hpp"
 
 namespace e2d
 {
     class atlas_asset final : public content_asset<atlas_asset, atlas> {
     public:
-        atlas_asset(content_type content)
-        : content_asset<atlas_asset, atlas>(std::move(content)) {}
-        static load_async_result load_async(library& library, str_view address);
+        static load_async_result load_async(const library& library, str_view address);
     };
 }
diff --git a/headers/enduro2d/high/assets/binary_asset.hpp b/headers/enduro2d/high/assets/binary_asset.hpp
index 612c5d25..17e40b95 100644
--- a/headers/enduro2d/high/assets/binary_asset.hpp
+++ b/headers/enduro2d/high/assets/binary_asset.hpp
@@ -7,14 +7,13 @@
 #pragma once
 
 #include "../_high.hpp"
+
 #include "../library.hpp"
 
 namespace e2d
 {
     class binary_asset final : public content_asset<binary_asset, buffer> {
     public:
-        binary_asset(content_type content)
-        : content_asset<binary_asset, buffer>(std::move(content)) {}
-        static load_async_result load_async(library& library, str_view address);
+        static load_async_result load_async(const library& library, str_view address);
     };
 }
diff --git a/headers/enduro2d/high/assets/flipbook_asset.hpp b/headers/enduro2d/high/assets/flipbook_asset.hpp
index 62c4c657..e9bd17d1 100644
--- a/headers/enduro2d/high/assets/flipbook_asset.hpp
+++ b/headers/enduro2d/high/assets/flipbook_asset.hpp
@@ -8,15 +8,13 @@
 
 #include "../_high.hpp"
 
-#include "../flipbook.hpp"
 #include "../library.hpp"
+#include "../flipbook.hpp"
 
 namespace e2d
 {
     class flipbook_asset final : public content_asset<flipbook_asset, flipbook> {
     public:
-        flipbook_asset(content_type content)
-        : content_asset<flipbook_asset, flipbook>(std::move(content)) {}
-        static load_async_result load_async(library& library, str_view address);
+        static load_async_result load_async(const library& library, str_view address);
     };
 }
diff --git a/headers/enduro2d/high/assets/image_asset.hpp b/headers/enduro2d/high/assets/image_asset.hpp
index 6d2f5f5c..99d88690 100644
--- a/headers/enduro2d/high/assets/image_asset.hpp
+++ b/headers/enduro2d/high/assets/image_asset.hpp
@@ -7,14 +7,13 @@
 #pragma once
 
 #include "../_high.hpp"
+
 #include "../library.hpp"
 
 namespace e2d
 {
     class image_asset final : public content_asset<image_asset, image> {
     public:
-        image_asset(content_type content)
-        : content_asset<image_asset, image>(std::move(content)) {}
-        static load_async_result load_async(library& library, str_view address);
+        static load_async_result load_async(const library& library, str_view address);
     };
 }
diff --git a/headers/enduro2d/high/assets/material_asset.hpp b/headers/enduro2d/high/assets/material_asset.hpp
index d0c1bc76..7d59e4d9 100644
--- a/headers/enduro2d/high/assets/material_asset.hpp
+++ b/headers/enduro2d/high/assets/material_asset.hpp
@@ -7,14 +7,13 @@
 #pragma once
 
 #include "../_high.hpp"
+
 #include "../library.hpp"
 
 namespace e2d
 {
     class material_asset final : public content_asset<material_asset, render::material> {
     public:
-        material_asset(content_type content)
-        : content_asset<material_asset, render::material>(std::move(content)) {}
-        static load_async_result load_async(library& library, str_view address);
+        static load_async_result load_async(const library& library, str_view address);
     };
 }
diff --git a/headers/enduro2d/high/assets/mesh_asset.hpp b/headers/enduro2d/high/assets/mesh_asset.hpp
index 074ef114..0fc294e5 100644
--- a/headers/enduro2d/high/assets/mesh_asset.hpp
+++ b/headers/enduro2d/high/assets/mesh_asset.hpp
@@ -7,14 +7,13 @@
 #pragma once
 
 #include "../_high.hpp"
+
 #include "../library.hpp"
 
 namespace e2d
 {
     class mesh_asset final : public content_asset<mesh_asset, mesh> {
     public:
-        mesh_asset(content_type content)
-        : content_asset<mesh_asset, mesh>(std::move(content)) {}
-        static load_async_result load_async(library& library, str_view address);
+        static load_async_result load_async(const library& library, str_view address);
     };
 }
diff --git a/headers/enduro2d/high/assets/model_asset.hpp b/headers/enduro2d/high/assets/model_asset.hpp
index c60f8db6..dc2cbb57 100644
--- a/headers/enduro2d/high/assets/model_asset.hpp
+++ b/headers/enduro2d/high/assets/model_asset.hpp
@@ -8,15 +8,13 @@
 
 #include "../_high.hpp"
 
-#include "../model.hpp"
 #include "../library.hpp"
+#include "../model.hpp"
 
 namespace e2d
 {
     class model_asset final : public content_asset<model_asset, model> {
     public:
-        model_asset(content_type content)
-        : content_asset<model_asset, model>(std::move(content)) {}
-        static load_async_result load_async(library& library, str_view address);
+        static load_async_result load_async(const library& library, str_view address);
     };
 }
diff --git a/headers/enduro2d/high/assets/shader_asset.hpp b/headers/enduro2d/high/assets/shader_asset.hpp
index ffde6928..a79cd031 100644
--- a/headers/enduro2d/high/assets/shader_asset.hpp
+++ b/headers/enduro2d/high/assets/shader_asset.hpp
@@ -7,14 +7,13 @@
 #pragma once
 
 #include "../_high.hpp"
+
 #include "../library.hpp"
 
 namespace e2d
 {
     class shader_asset final : public content_asset<shader_asset, shader_ptr> {
     public:
-        shader_asset(content_type content)
-        : content_asset<shader_asset, shader_ptr>(std::move(content)) {}
-        static load_async_result load_async(library& library, str_view address);
+        static load_async_result load_async(const library& library, str_view address);
     };
 }
diff --git a/headers/enduro2d/high/assets/shape_asset.hpp b/headers/enduro2d/high/assets/shape_asset.hpp
index 4c7bd758..f949f41d 100644
--- a/headers/enduro2d/high/assets/shape_asset.hpp
+++ b/headers/enduro2d/high/assets/shape_asset.hpp
@@ -7,14 +7,13 @@
 #pragma once
 
 #include "../_high.hpp"
+
 #include "../library.hpp"
 
 namespace e2d
 {
     class shape_asset final : public content_asset<shape_asset, shape> {
     public:
-        shape_asset(content_type content)
-        : content_asset<shape_asset, shape>(std::move(content)) {}
-        static load_async_result load_async(library& library, str_view address);
+        static load_async_result load_async(const library& library, str_view address);
     };
 }
diff --git a/headers/enduro2d/high/assets/sprite_asset.hpp b/headers/enduro2d/high/assets/sprite_asset.hpp
index f00f2f9c..86ed8f20 100644
--- a/headers/enduro2d/high/assets/sprite_asset.hpp
+++ b/headers/enduro2d/high/assets/sprite_asset.hpp
@@ -8,15 +8,13 @@
 
 #include "../_high.hpp"
 
-#include "../sprite.hpp"
 #include "../library.hpp"
+#include "../sprite.hpp"
 
 namespace e2d
 {
     class sprite_asset final : public content_asset<sprite_asset, sprite> {
     public:
-        sprite_asset(content_type content)
-        : content_asset<sprite_asset, sprite>(std::move(content)) {}
-        static load_async_result load_async(library& library, str_view address);
+        static load_async_result load_async(const library& library, str_view address);
     };
 }
diff --git a/headers/enduro2d/high/assets/text_asset.hpp b/headers/enduro2d/high/assets/text_asset.hpp
index 9e001684..49a3f3da 100644
--- a/headers/enduro2d/high/assets/text_asset.hpp
+++ b/headers/enduro2d/high/assets/text_asset.hpp
@@ -7,14 +7,13 @@
 #pragma once
 
 #include "../_high.hpp"
+
 #include "../library.hpp"
 
 namespace e2d
 {
     class text_asset final : public content_asset<text_asset, str> {
     public:
-        text_asset(content_type content)
-        : content_asset<text_asset, str>(std::move(content)) {}
-        static load_async_result load_async(library& library, str_view address);
+        static load_async_result load_async(const library& library, str_view address);
     };
 }
diff --git a/headers/enduro2d/high/assets/texture_asset.hpp b/headers/enduro2d/high/assets/texture_asset.hpp
index 50f4157f..6715490b 100644
--- a/headers/enduro2d/high/assets/texture_asset.hpp
+++ b/headers/enduro2d/high/assets/texture_asset.hpp
@@ -7,14 +7,13 @@
 #pragma once
 
 #include "../_high.hpp"
+
 #include "../library.hpp"
 
 namespace e2d
 {
     class texture_asset final : public content_asset<texture_asset, texture_ptr> {
     public:
-        texture_asset(content_type content)
-        : content_asset<texture_asset, texture_ptr>(std::move(content)) {}
-        static load_async_result load_async(library& library, str_view address);
+        static load_async_result load_async(const library& library, str_view address);
     };
 }
diff --git a/headers/enduro2d/high/library.hpp b/headers/enduro2d/high/library.hpp
index a1f50eaf..72f81716 100644
--- a/headers/enduro2d/high/library.hpp
+++ b/headers/enduro2d/high/library.hpp
@@ -10,6 +10,9 @@
 
 #include "_high.hpp"
 
+#include "asset.hpp"
+#include "address.hpp"
+
 namespace e2d
 {
     //
@@ -23,54 +26,6 @@ namespace e2d
         }
     };
 
-    //
-    // asset_loading_exception
-    //
-
-    class asset_loading_exception : public exception {
-        const char* what() const noexcept override = 0;
-    };
-
-    //
-    // content_asset_base
-    //
-
-    class content_asset_base
-        : private noncopyable
-        , public ref_counter<content_asset_base> {
-    public:
-        content_asset_base() = default;
-        virtual ~content_asset_base() noexcept = default;
-    };
-
-    //
-    // content_asset
-    //
-
-    template < typename Asset, typename Content >
-    class content_asset : public content_asset_base {
-    public:
-        using asset_type = Asset;
-        using content_type = Content;
-
-        using ptr = intrusive_ptr<Asset>;
-        using load_result = intrusive_ptr<Asset>;
-        using load_async_result = stdex::promise<load_result>;
-    public:
-        static load_result create(Content content) {
-            return load_result(new Asset(std::move(content)));
-        }
-
-        content_asset(Content content)
-        : content_(std::move(content)) {}
-
-        const Content& content() const noexcept {
-            return content_;
-        }
-    private:
-        Content content_;
-    };
-
     //
     // library
     //
@@ -84,55 +39,19 @@ namespace e2d
         std::size_t unload_unused_assets() noexcept;
 
         template < typename Asset >
-        typename Asset::load_result load_asset(str_view address);
+        typename Asset::load_result load_main_asset(str_view address) const;
 
         template < typename Asset >
-        typename Asset::load_async_result load_asset_async(str_view address);
+        typename Asset::load_async_result load_main_asset_async(str_view address) const;
+
+        template < typename Asset, typename Nested = Asset >
+        typename Nested::load_result load_asset(str_view address) const;
+
+        template < typename Asset, typename Nested = Asset >
+        typename Nested::load_async_result load_asset_async(str_view address) const;
     private:
         url root_;
     };
-
-    //
-    // asset_cache_base
-    //
-
-    class asset_cache_base : private noncopyable {
-    public:
-        asset_cache_base();
-        virtual ~asset_cache_base() noexcept;
-
-        static std::size_t unload_all_unused_assets() noexcept;
-        virtual std::size_t unload_self_unused_assets() noexcept = 0;
-    private:
-        static std::mutex mutex_;
-        static hash_set<asset_cache_base*> caches_;
-    };
-
-    //
-    // asset_cache
-    //
-
-    template < typename Asset >
-    class asset_cache : public asset_cache_base
-                      , public module<asset_cache<Asset>> {
-    public:
-        using asset_result = typename Asset::load_result;
-    public:
-        asset_cache(library& l);
-        ~asset_cache() noexcept final;
-
-        asset_result find(str_hash address) const;
-        void store(str_hash address, const asset_result& asset);
-
-        void clear() noexcept;
-        std::size_t asset_count() const noexcept;
-
-        std::size_t unload_self_unused_assets() noexcept override;
-    private:
-        library& library_;
-        mutable std::mutex mutex_;
-        hash_map<str_hash, asset_result> assets_;
-    };
 }
 
 #include "library.inl"
diff --git a/headers/enduro2d/high/library.inl b/headers/enduro2d/high/library.inl
index 8d01792e..edf4b579 100644
--- a/headers/enduro2d/high/library.inl
+++ b/headers/enduro2d/high/library.inl
@@ -13,13 +13,9 @@
 
 namespace e2d
 {
-    //
-    // library
-    //
-
     template < typename Asset >
-    typename Asset::load_result library::load_asset(str_view address) {
-        auto p = load_asset_async<Asset>(address);
+    typename Asset::load_result library::load_main_asset(str_view address) const {
+        auto p = load_main_asset_async<Asset>(address);
 
         if ( modules::is_initialized<deferrer>() ) {
             the<deferrer>().active_safe_wait_promise(p);
@@ -29,77 +25,61 @@ namespace e2d
     }
 
     template < typename Asset >
-    typename Asset::load_async_result library::load_asset_async(str_view address) {
+    typename Asset::load_async_result library::load_main_asset_async(str_view address) const {
+        const auto main_address = address::parent(address);
+        const auto main_address_hash = make_hash(main_address);
+
         if ( !modules::is_initialized<asset_cache<Asset>>() ) {
-            return Asset::load_async(*this, address);
+            return Asset::load_async(*this, main_address);
         }
 
         auto& cache = the<asset_cache<Asset>>();
-        if ( auto cached_asset = cache.find(address) ) {
+        if ( auto cached_asset = cache.find(main_address_hash) ) {
             return stdex::make_resolved_promise(std::move(cached_asset));
         }
 
-        return Asset::load_async(*this, address)
+        return Asset::load_async(*this, main_address)
             .then([
                 &cache,
-                address_hash = make_hash(address)
-            ](auto&& new_asset){
-                cache.store(address_hash, new_asset);
-                return std::forward<decltype(new_asset)>(new_asset);
+                main_address_hash
+            ](const typename Asset::load_result& new_asset){
+                cache.store(main_address_hash, new_asset);
+                return new_asset;
             });
     }
 
-    //
-    // asset_cache
-    //
+    template < typename Asset, typename Nested >
+    typename Nested::load_result library::load_asset(str_view address) const {
+        auto p = load_asset_async<Asset, Nested>(address);
 
-    template < typename T >
-    asset_cache<T>::asset_cache(library& l)
-    : library_(l) {}
-
-    template < typename T >
-    asset_cache<T>::~asset_cache() noexcept = default;
-
-    template < typename T >
-    typename asset_cache<T>::asset_result asset_cache<T>::find(str_hash address) const {
-        std::lock_guard<std::mutex> guard(mutex_);
-        const auto iter = assets_.find(address);
-        return iter != assets_.end()
-            ? iter->second
-            : nullptr;
-    }
-
-    template < typename T >
-    void asset_cache<T>::store(str_hash address, const asset_result& asset) {
-        std::lock_guard<std::mutex> guard(mutex_);
-        assets_[address] = asset;
-    }
-
-    template < typename T >
-    void asset_cache<T>::clear() noexcept {
-        std::lock_guard<std::mutex> guard(mutex_);
-        assets_.clear();
-    }
-
-    template < typename T >
-    std::size_t asset_cache<T>::asset_count() const noexcept {
-        std::lock_guard<std::mutex> guard(mutex_);
-        return assets_.size();
-    }
-
-    template < typename T >
-    std::size_t asset_cache<T>::unload_self_unused_assets() noexcept {
-        std::lock_guard<std::mutex> guard(mutex_);
-        std::size_t result = 0u;
-        for ( auto iter = assets_.begin(); iter != assets_.end(); ) {
-            if ( !iter->second || 1 == iter->second->use_count() ) {
-                iter = assets_.erase(iter);
-                ++result;
-            } else {
-                ++iter;
-            }
+        if ( modules::is_initialized<deferrer>() ) {
+            the<deferrer>().active_safe_wait_promise(p);
         }
-        return result;
+
+        return p.get_or_default(nullptr);
+    }
+
+    template < typename Asset, typename Nested >
+    typename Nested::load_async_result library::load_asset_async(str_view address) const {
+        return load_main_asset_async<Asset>(address::parent(address))
+            .then([
+                address = str(address)
+            ](const typename Asset::load_result& main_asset){
+                asset_ptr nested_asset = main_asset;
+                str nested_address = address::nested(address);
+
+                while ( nested_asset && !nested_address.empty() ) {
+                    nested_asset = nested_asset->find_nested_asset(address::parent(nested_address));
+                    nested_address = address::nested(nested_address);
+                }
+
+                using nested_asset_type = typename Nested::asset_type;
+                if ( auto result = dynamic_pointer_cast<nested_asset_type>(nested_asset) ) {
+                    return result;
+                }
+
+                throw asset_loading_exception();
+            });
     }
 }
 
diff --git a/headers/enduro2d/high/sprite.hpp b/headers/enduro2d/high/sprite.hpp
index 3b9d074a..f1d178f8 100644
--- a/headers/enduro2d/high/sprite.hpp
+++ b/headers/enduro2d/high/sprite.hpp
@@ -40,7 +40,6 @@ namespace e2d
         const texture_asset::ptr& texture() const noexcept;
         const material_asset::ptr& material() const noexcept;
     private:
-        v2f size_;
         v2f pivot_;
         b2f texrect_;
         texture_asset::ptr texture_;
diff --git a/sources/enduro2d/high/address.cpp b/sources/enduro2d/high/address.cpp
new file mode 100644
index 00000000..c676c3c7
--- /dev/null
+++ b/sources/enduro2d/high/address.cpp
@@ -0,0 +1,39 @@
+/*******************************************************************************
+ * This file is part of the "Enduro2D"
+ * For conditions of distribution and use, see copyright notice in LICENSE.md
+ * Copyright (C) 2018-2019 Matvey Cherevko
+ ******************************************************************************/
+
+#include <enduro2d/high/address.hpp>
+
+namespace
+{
+    using namespace e2d;
+
+    const str_view address_separator = ":/";
+
+    str_view::iterator str_view_search(str_view str, str_view s_str) noexcept {
+        return std::search(str.begin(), str.end(), s_str.begin(), s_str.end());
+    }
+}
+
+namespace e2d { namespace address
+{
+    str parent(str_view address) {
+        const auto sep_e = str_view_search(address, address_separator);
+        if ( sep_e == address.end() ) {
+            return address;
+        }
+        const auto sep_d = std::distance(address.begin(), sep_e);
+        return address.substr(0, static_cast<std::size_t>(sep_d));
+    }
+
+    str nested(str_view address) {
+        const auto sep_e = str_view_search(address, address_separator);
+        if ( sep_e == address.end() ) {
+            return str();
+        }
+        const auto sep_d = std::distance(address.begin(), sep_e);
+        return address.substr(static_cast<std::size_t>(sep_d) + address_separator.size());
+    }
+}}
diff --git a/sources/enduro2d/high/asset.cpp b/sources/enduro2d/high/asset.cpp
new file mode 100644
index 00000000..25d77626
--- /dev/null
+++ b/sources/enduro2d/high/asset.cpp
@@ -0,0 +1,49 @@
+/*******************************************************************************
+ * This file is part of the "Enduro2D"
+ * For conditions of distribution and use, see copyright notice in LICENSE.md
+ * Copyright (C) 2018-2019 Matvey Cherevko
+ ******************************************************************************/
+
+#include <enduro2d/high/asset.hpp>
+
+namespace e2d
+{
+    //
+    // asset
+    //
+
+    asset::asset() = default;
+    asset::~asset() noexcept = default;
+
+    //
+    // asset_cache_base
+    //
+
+    std::mutex asset_cache_base::mutex_;
+    hash_set<asset_cache_base*> asset_cache_base::caches_;
+
+    asset_cache_base::asset_cache_base() {
+        std::lock_guard<std::mutex> guard(mutex_);
+        caches_.insert(this);
+    }
+
+    asset_cache_base::~asset_cache_base() noexcept {
+        std::lock_guard<std::mutex> guard(mutex_);
+        caches_.erase(this);
+    }
+
+    std::size_t asset_cache_base::unload_all_unused_assets() noexcept {
+        std::lock_guard<std::mutex> guard(mutex_);
+        return std::accumulate(caches_.begin(), caches_.end(), std::size_t(0),
+            [](std::size_t acc, asset_cache_base* cache){
+                return acc + cache->unload_self_unused_assets();
+            });
+    }
+
+    //
+    // asset_factory
+    //
+
+    asset_factory::asset_factory() = default;
+    asset_factory::~asset_factory() noexcept = default;
+}
diff --git a/sources/enduro2d/high/assets/atlas_asset.cpp b/sources/enduro2d/high/assets/atlas_asset.cpp
index a9e48c18..d800f71e 100644
--- a/sources/enduro2d/high/assets/atlas_asset.cpp
+++ b/sources/enduro2d/high/assets/atlas_asset.cpp
@@ -145,7 +145,7 @@ namespace
     }
 
     stdex::promise<atlas> parse_atlas(
-        library& library,
+        const library& library,
         str_view parent_address,
         const rapidjson::Value& root)
     {
@@ -187,7 +187,7 @@ namespace
 namespace e2d
 {
     atlas_asset::load_async_result atlas_asset::load_async(
-        library& library, str_view address)
+        const library& library, str_view address)
     {
         return library.load_asset_async<json_asset>(address)
         .then([
diff --git a/sources/enduro2d/high/assets/binary_asset.cpp b/sources/enduro2d/high/assets/binary_asset.cpp
index ed321b77..b989a25d 100644
--- a/sources/enduro2d/high/assets/binary_asset.cpp
+++ b/sources/enduro2d/high/assets/binary_asset.cpp
@@ -20,7 +20,7 @@ namespace
 namespace e2d
 {
     binary_asset::load_async_result binary_asset::load_async(
-        library& library, str_view address)
+        const library& library, str_view address)
     {
         const auto asset_url = library.root() / address;
         return the<vfs>().load_async(asset_url)
diff --git a/sources/enduro2d/high/assets/flipbook_asset.cpp b/sources/enduro2d/high/assets/flipbook_asset.cpp
index 3d71789c..d3a7c8d5 100644
--- a/sources/enduro2d/high/assets/flipbook_asset.cpp
+++ b/sources/enduro2d/high/assets/flipbook_asset.cpp
@@ -107,7 +107,7 @@ namespace
     }
 
     stdex::promise<flipbook::frame> parse_flipbook_atlas_frame(
-        library& library,
+        const library& library,
         str_view parent_address,
         const rapidjson::Value& root)
     {
@@ -140,7 +140,7 @@ namespace
     }
 
     stdex::promise<flipbook::frame> parse_flipbook_texture_frame(
-        library& library,
+        const library& library,
         str_view parent_address,
         const rapidjson::Value& root)
     {
@@ -174,7 +174,7 @@ namespace
     }
 
     stdex::promise<flipbook::frame> parse_flipbook_frame(
-        library& library,
+        const library& library,
         str_view parent_address,
         const rapidjson::Value& root)
     {
@@ -191,7 +191,7 @@ namespace
     }
 
     stdex::promise<vector<flipbook::frame>> parse_flipbook_frames(
-        library& library,
+        const library& library,
         str_view parent_address,
         const rapidjson::Value& root)
     {
@@ -245,7 +245,7 @@ namespace
     }
 
     stdex::promise<flipbook> parse_flipbook(
-        library& library,
+        const library& library,
         str_view parent_address,
         const rapidjson::Value& root)
     {
@@ -290,7 +290,7 @@ namespace
 namespace e2d
 {
     flipbook_asset::load_async_result flipbook_asset::load_async(
-        library& library, str_view address)
+        const library& library, str_view address)
     {
         return library.load_asset_async<json_asset>(address)
         .then([
diff --git a/sources/enduro2d/high/assets/image_asset.cpp b/sources/enduro2d/high/assets/image_asset.cpp
index a86f10bf..93747a15 100644
--- a/sources/enduro2d/high/assets/image_asset.cpp
+++ b/sources/enduro2d/high/assets/image_asset.cpp
@@ -21,7 +21,7 @@ namespace
 namespace e2d
 {
     image_asset::load_async_result image_asset::load_async(
-        library& library, str_view address)
+        const library& library, str_view address)
     {
         return library.load_asset_async<binary_asset>(address)
             .then([](const binary_asset::load_result& image_data){
diff --git a/sources/enduro2d/high/assets/json_asset.cpp b/sources/enduro2d/high/assets/json_asset.cpp
index 689d8fa2..bd53b749 100644
--- a/sources/enduro2d/high/assets/json_asset.cpp
+++ b/sources/enduro2d/high/assets/json_asset.cpp
@@ -22,7 +22,7 @@ namespace
 namespace e2d
 {
     json_asset::load_async_result json_asset::load_async(
-        library& library, str_view address)
+        const library& library, str_view address)
     {
         return library.load_asset_async<text_asset>(address)
             .then([](const text_asset::load_result& json_data){
diff --git a/sources/enduro2d/high/assets/json_asset.hpp b/sources/enduro2d/high/assets/json_asset.hpp
index 60dd7ec1..f05e963b 100644
--- a/sources/enduro2d/high/assets/json_asset.hpp
+++ b/sources/enduro2d/high/assets/json_asset.hpp
@@ -15,6 +15,6 @@ namespace e2d
     class json_asset final : public content_asset<json_asset, rapidjson::Document> {
     public:
         using content_asset<json_asset, rapidjson::Document>::content_asset;
-        static load_async_result load_async(library& library, str_view address);
+        static load_async_result load_async(const library& library, str_view address);
     };
 }
diff --git a/sources/enduro2d/high/assets/material_asset.cpp b/sources/enduro2d/high/assets/material_asset.cpp
index 02c96e53..9b8d979f 100644
--- a/sources/enduro2d/high/assets/material_asset.cpp
+++ b/sources/enduro2d/high/assets/material_asset.cpp
@@ -492,7 +492,7 @@ namespace
     }
 
     stdex::promise<shader_ptr> parse_shader_block(
-        library& library,
+        const library& library,
         str_view parent_address,
         const rapidjson::Value& root)
     {
@@ -506,7 +506,7 @@ namespace
     }
 
     stdex::promise<texture_ptr> parse_texture_block(
-        library& library,
+        const library& library,
         str_view parent_address,
         const rapidjson::Value& root)
     {
@@ -520,7 +520,7 @@ namespace
     }
 
     stdex::promise<std::pair<str_hash,render::sampler_state>> parse_sampler_state(
-        library& library,
+        const library& library,
         str_view parent_address,
         const rapidjson::Value& root)
     {
@@ -669,7 +669,7 @@ namespace
     }
 
     stdex::promise<render::property_block> parse_property_block(
-        library& library,
+        const library& library,
         str_view parent_address,
         const rapidjson::Value& root)
     {
@@ -1092,7 +1092,7 @@ namespace
     }
 
     stdex::promise<render::pass_state> parse_pass_state(
-        library& library,
+        const library& library,
         str_view parent_address,
         const rapidjson::Value& root)
     {
@@ -1126,7 +1126,7 @@ namespace
     }
 
     stdex::promise<render::material> parse_material(
-        library& library,
+        const library& library,
         str_view parent_address,
         const rapidjson::Value& root)
     {
@@ -1169,7 +1169,7 @@ namespace
 namespace e2d
 {
     material_asset::load_async_result material_asset::load_async(
-        library& library, str_view address)
+        const library& library, str_view address)
     {
         return library.load_asset_async<json_asset>(address)
             .then([
diff --git a/sources/enduro2d/high/assets/mesh_asset.cpp b/sources/enduro2d/high/assets/mesh_asset.cpp
index 660a396b..7d7b90ea 100644
--- a/sources/enduro2d/high/assets/mesh_asset.cpp
+++ b/sources/enduro2d/high/assets/mesh_asset.cpp
@@ -21,7 +21,7 @@ namespace
 namespace e2d
 {
     mesh_asset::load_async_result mesh_asset::load_async(
-        library& library, str_view address)
+        const library& library, str_view address)
     {
         return library.load_asset_async<binary_asset>(address)
             .then([](const binary_asset::load_result& mesh_data){
diff --git a/sources/enduro2d/high/assets/model_asset.cpp b/sources/enduro2d/high/assets/model_asset.cpp
index 6f95b408..18fa6dd6 100644
--- a/sources/enduro2d/high/assets/model_asset.cpp
+++ b/sources/enduro2d/high/assets/model_asset.cpp
@@ -51,7 +51,7 @@ namespace
     }
 
     stdex::promise<model> parse_model(
-        library& library,
+        const library& library,
         str_view parent_address,
         const rapidjson::Value& root)
     {
@@ -97,7 +97,7 @@ namespace
 namespace e2d
 {
     model_asset::load_async_result model_asset::load_async(
-        library& library, str_view address)
+        const library& library, str_view address)
     {
         return library.load_asset_async<json_asset>(address)
         .then([
diff --git a/sources/enduro2d/high/assets/shader_asset.cpp b/sources/enduro2d/high/assets/shader_asset.cpp
index d9a66921..b77bc9d7 100644
--- a/sources/enduro2d/high/assets/shader_asset.cpp
+++ b/sources/enduro2d/high/assets/shader_asset.cpp
@@ -49,7 +49,7 @@ namespace
     }
 
     stdex::promise<shader_ptr> parse_shader(
-        library& library,
+        const library& library,
         str_view parent_address,
         const rapidjson::Value& root)
     {
@@ -84,7 +84,7 @@ namespace
 namespace e2d
 {
     shader_asset::load_async_result shader_asset::load_async(
-        library& library, str_view address)
+        const library& library, str_view address)
     {
         return library.load_asset_async<json_asset>(address)
             .then([
diff --git a/sources/enduro2d/high/assets/shape_asset.cpp b/sources/enduro2d/high/assets/shape_asset.cpp
index b19abcf2..69495697 100644
--- a/sources/enduro2d/high/assets/shape_asset.cpp
+++ b/sources/enduro2d/high/assets/shape_asset.cpp
@@ -21,7 +21,7 @@ namespace
 namespace e2d
 {
     shape_asset::load_async_result shape_asset::load_async(
-        library& library, str_view address)
+        const library& library, str_view address)
     {
         return library.load_asset_async<binary_asset>(address)
             .then([](const binary_asset::load_result& shape_data){
diff --git a/sources/enduro2d/high/assets/sprite_asset.cpp b/sources/enduro2d/high/assets/sprite_asset.cpp
index 48e50e6d..debc72e7 100644
--- a/sources/enduro2d/high/assets/sprite_asset.cpp
+++ b/sources/enduro2d/high/assets/sprite_asset.cpp
@@ -78,7 +78,7 @@ namespace
     }
 
     stdex::promise<sprite> parse_sprite_with_atlas(
-        library& library,
+        const library& library,
         str_view parent_address,
         const rapidjson::Value& root)
     {
@@ -130,7 +130,7 @@ namespace
     }
 
     stdex::promise<sprite> parse_sprite_with_texture(
-        library& library,
+        const library& library,
         str_view parent_address,
         const rapidjson::Value& root)
     {
@@ -183,7 +183,7 @@ namespace
     }
 
     stdex::promise<sprite> parse_sprite(
-        library& library,
+        const library& library,
         str_view parent_address,
         const rapidjson::Value& root)
     {
@@ -203,7 +203,7 @@ namespace
 namespace e2d
 {
     sprite_asset::load_async_result sprite_asset::load_async(
-        library& library, str_view address)
+        const library& library, str_view address)
     {
         return library.load_asset_async<json_asset>(address)
         .then([
diff --git a/sources/enduro2d/high/assets/text_asset.cpp b/sources/enduro2d/high/assets/text_asset.cpp
index ebd2db73..10a7b17e 100644
--- a/sources/enduro2d/high/assets/text_asset.cpp
+++ b/sources/enduro2d/high/assets/text_asset.cpp
@@ -20,7 +20,7 @@ namespace
 namespace e2d
 {
     text_asset::load_async_result text_asset::load_async(
-        library& library, str_view address)
+        const library& library, str_view address)
     {
         const auto asset_url = library.root() / address;
         return the<vfs>().load_as_string_async(asset_url)
diff --git a/sources/enduro2d/high/assets/texture_asset.cpp b/sources/enduro2d/high/assets/texture_asset.cpp
index 55430ef8..2bbbc066 100644
--- a/sources/enduro2d/high/assets/texture_asset.cpp
+++ b/sources/enduro2d/high/assets/texture_asset.cpp
@@ -21,7 +21,7 @@ namespace
 namespace e2d
 {
     texture_asset::load_async_result texture_asset::load_async(
-        library& library, str_view address)
+        const library& library, str_view address)
     {
         return library.load_asset_async<image_asset>(address)
             .then([](const image_asset::load_result& texture_data){
diff --git a/sources/enduro2d/high/assets/xml_asset.cpp b/sources/enduro2d/high/assets/xml_asset.cpp
index 89e6f6ce..eba09db4 100644
--- a/sources/enduro2d/high/assets/xml_asset.cpp
+++ b/sources/enduro2d/high/assets/xml_asset.cpp
@@ -22,7 +22,7 @@ namespace
 namespace e2d
 {
     xml_asset::load_async_result xml_asset::load_async(
-        library& library, str_view address)
+        const library& library, str_view address)
     {
         return library.load_asset_async<text_asset>(address)
             .then([](const text_asset::load_result& xml_data){
diff --git a/sources/enduro2d/high/assets/xml_asset.hpp b/sources/enduro2d/high/assets/xml_asset.hpp
index 6c640c54..2ffd45c3 100644
--- a/sources/enduro2d/high/assets/xml_asset.hpp
+++ b/sources/enduro2d/high/assets/xml_asset.hpp
@@ -15,6 +15,6 @@ namespace e2d
     class xml_asset final : public content_asset<xml_asset, pugi::xml_document> {
     public:
         using content_asset<xml_asset, pugi::xml_document>::content_asset;
-        static load_async_result load_async(library& library, str_view address);
+        static load_async_result load_async(const library& library, str_view address);
     };
 }
diff --git a/sources/enduro2d/high/library.cpp b/sources/enduro2d/high/library.cpp
index 4fc83c1e..08e9ed1a 100644
--- a/sources/enduro2d/high/library.cpp
+++ b/sources/enduro2d/high/library.cpp
@@ -6,17 +6,8 @@
 
 #include <enduro2d/high/library.hpp>
 
-namespace
-{
-    using namespace e2d;
-}
-
 namespace e2d
 {
-    //
-    // library
-    //
-
     library::library(const url& root)
     : root_(root) {}
 
@@ -29,29 +20,4 @@ namespace e2d
     std::size_t library::unload_unused_assets() noexcept {
         return asset_cache_base::unload_all_unused_assets();
     }
-
-    //
-    // asset_cache_base
-    //
-
-    std::mutex asset_cache_base::mutex_;
-    hash_set<asset_cache_base*> asset_cache_base::caches_;
-
-    asset_cache_base::asset_cache_base() {
-        std::lock_guard<std::mutex> guard(mutex_);
-        caches_.insert(this);
-    }
-
-    asset_cache_base::~asset_cache_base() noexcept {
-        std::lock_guard<std::mutex> guard(mutex_);
-        caches_.erase(this);
-    }
-
-    std::size_t asset_cache_base::unload_all_unused_assets() noexcept {
-        std::lock_guard<std::mutex> guard(mutex_);
-        return std::accumulate( caches_.begin(), caches_.end(), std::size_t(0),
-            [](std::size_t acc, asset_cache_base* cache){
-                return acc + cache->unload_self_unused_assets();
-            });
-    }
 }
diff --git a/sources/enduro2d/high/sprite.cpp b/sources/enduro2d/high/sprite.cpp
index 65676103..f8773757 100644
--- a/sources/enduro2d/high/sprite.cpp
+++ b/sources/enduro2d/high/sprite.cpp
@@ -28,7 +28,6 @@ namespace e2d
     }
 
     void sprite::clear() noexcept {
-        size_ = v2f::zero();
         pivot_ = v2f::zero();
         texrect_ = b2f::zero();
         texture_.reset();
@@ -37,7 +36,6 @@ namespace e2d
 
     void sprite::swap(sprite& other) noexcept {
         using std::swap;
-        swap(size_, other.size_);
         swap(pivot_, other.pivot_);
         swap(texrect_, other.texrect_);
         swap(texture_, other.texture_);
@@ -55,7 +53,6 @@ namespace e2d
     sprite& sprite::assign(const sprite& other) {
         if ( this != &other ) {
             sprite s;
-            s.size_ = other.size_;
             s.pivot_ = other.pivot_;
             s.texrect_ = other.texrect_;
             s.texture_ = other.texture_;
diff --git a/sources/enduro2d/high/starter.cpp b/sources/enduro2d/high/starter.cpp
index 060ae459..d9829fe6 100644
--- a/sources/enduro2d/high/starter.cpp
+++ b/sources/enduro2d/high/starter.cpp
@@ -28,10 +28,10 @@ namespace
     using namespace e2d;
 
     template < typename Module, typename... Args >
-    void safe_module_initialize(Args&&... args) {
-        if ( !modules::is_initialized<Module>() ) {
-            modules::initialize<Module>(std::forward<Args>(args)...);
-        }
+    Module& safe_module_initialize(Args&&... args) {
+        return modules::is_initialized<Module>()
+            ? modules::instance<Module>()
+            : modules::initialize<Module>(std::forward<Args>(args)...);
     }
 
     class starter_application final : public application {
@@ -137,11 +137,24 @@ namespace e2d
         safe_module_initialize<asset_cache<sprite_asset>>(the<library>());
         safe_module_initialize<asset_cache<text_asset>>(the<library>());
         safe_module_initialize<asset_cache<texture_asset>>(the<library>());
+        safe_module_initialize<asset_factory>()
+            .register_asset<atlas_asset>("atlas")
+            .register_asset<binary_asset>("binary")
+            .register_asset<image_asset>("image")
+            .register_asset<material_asset>("material")
+            .register_asset<mesh_asset>("mesh")
+            .register_asset<model_asset>("model")
+            .register_asset<shader_asset>("shader")
+            .register_asset<shape_asset>("shape")
+            .register_asset<sprite_asset>("sprite")
+            .register_asset<text_asset>("text")
+            .register_asset<texture_asset>("texture");
         safe_module_initialize<world>();
     }
 
     starter::~starter() noexcept {
         modules::shutdown<world>();
+        modules::shutdown<asset_factory>();
         modules::shutdown<asset_cache<texture_asset>>();
         modules::shutdown<asset_cache<text_asset>>();
         modules::shutdown<asset_cache<sprite_asset>>();
diff --git a/untests/sources/untests_high/address.cpp b/untests/sources/untests_high/address.cpp
new file mode 100644
index 00000000..231b6c60
--- /dev/null
+++ b/untests/sources/untests_high/address.cpp
@@ -0,0 +1,31 @@
+/*******************************************************************************
+ * This file is part of the "Enduro2D"
+ * For conditions of distribution and use, see copyright notice in LICENSE.md
+ * Copyright (C) 2018-2019 Matvey Cherevko
+ ******************************************************************************/
+
+#include "_high.hpp"
+using namespace e2d;
+
+TEST_CASE("address") {
+    SECTION("parent") {
+        REQUIRE(address::parent("") == "");
+        REQUIRE(address::parent(":/") == "");
+        REQUIRE(address::parent(":/child") == "");
+        REQUIRE(address::parent("at/las.json") == "at/las.json");
+        REQUIRE(address::parent("at/las.json:/") == "at/las.json");
+        REQUIRE(address::parent("at/las.json:/spr/ite.png") == "at/las.json");
+        REQUIRE(address::parent("at/las.json:/spr/ite.png:/") == "at/las.json");
+        REQUIRE(address::parent("at/las.json:/spr/ite.png:/child") == "at/las.json");
+    }
+    SECTION("nested") {
+        REQUIRE(address::nested("") == "");
+        REQUIRE(address::nested(":/") == "");
+        REQUIRE(address::nested(":/chi/ld") == "chi/ld");
+        REQUIRE(address::nested("at/las.json") == "");
+        REQUIRE(address::nested("at/las.json:/") == "");
+        REQUIRE(address::nested("at/las.json:/spr/ite.png") == "spr/ite.png");
+        REQUIRE(address::nested("at/las.json:/spr/ite.png:/") == "spr/ite.png:/");
+        REQUIRE(address::nested("at/las.json:/spr/ite.png:/chi/ld") == "spr/ite.png:/chi/ld");
+    }
+}
diff --git a/untests/sources/untests_high/asset.cpp b/untests/sources/untests_high/asset.cpp
new file mode 100644
index 00000000..26fe03db
--- /dev/null
+++ b/untests/sources/untests_high/asset.cpp
@@ -0,0 +1,79 @@
+/*******************************************************************************
+ * This file is part of the "Enduro2D"
+ * For conditions of distribution and use, see copyright notice in LICENSE.md
+ * Copyright (C) 2018-2019 Matvey Cherevko
+ ******************************************************************************/
+
+#include "_high.hpp"
+using namespace e2d;
+
+namespace
+{
+    class safe_starter_initializer final : private noncopyable {
+    public:
+        safe_starter_initializer() {
+            modules::initialize<starter>(0, nullptr,
+                starter::parameters(
+                    engine::parameters("asset_untests", "enduro2d")
+                        .without_graphics(true)));
+        }
+
+        ~safe_starter_initializer() noexcept {
+            modules::shutdown<starter>();
+        }
+    };
+
+    class fake_nested_asset final : public content_asset<fake_nested_asset, int> {
+    };
+
+    class fake_asset final : public content_asset<fake_asset, int> {
+    public:
+        static load_async_result load_async(const library& library, str_view address) {
+            E2D_UNUSED(library);
+            return address == "42"
+                ? stdex::make_resolved_promise(fake_asset::create(42, {
+                    {"21", fake_nested_asset::create(21, {
+                        {"2", fake_nested_asset::create(2)}
+                    })},
+                    {"84", fake_nested_asset::create(84, {
+                        {"8", fake_nested_asset::create(8)}
+                    })}
+                }))
+                : stdex::make_rejected_promise<load_result>(asset_loading_exception());
+        }
+    };
+}
+
+TEST_CASE("asset"){
+    safe_starter_initializer initializer;
+    library& l = the<library>();
+    {
+        REQUIRE_FALSE(l.load_asset<fake_asset>("none"));
+
+        auto fa = l.load_asset<fake_asset>("42");
+        REQUIRE(fa);
+        REQUIRE(fa->content() == 42);
+
+        REQUIRE_FALSE(fa->find_nested_asset("none"));
+        REQUIRE(fa->find_nested_asset("21"));
+        REQUIRE_FALSE(fa->find_nested_asset<binary_asset>("21"));
+        REQUIRE(fa->find_nested_asset<fake_nested_asset>("21"));
+        REQUIRE(fa->find_nested_asset<fake_nested_asset>("21")->content() == 21);
+        REQUIRE(fa->find_nested_asset<fake_nested_asset>("84")->content() == 84);
+    }
+    {
+        REQUIRE(l.load_asset<fake_asset, fake_nested_asset>("42:/21"));
+        REQUIRE(l.load_asset<fake_asset, fake_nested_asset>("42:/21")->content() == 21);
+
+        REQUIRE_FALSE(l.load_asset<fake_asset, binary_asset>("42:/21"));
+        REQUIRE_FALSE(l.load_asset<fake_asset, fake_nested_asset>("42:/none"));
+        REQUIRE_FALSE(l.load_asset<fake_asset, fake_nested_asset>("42:/none:/21"));
+
+        REQUIRE(l.load_asset<fake_asset, fake_nested_asset>("42:/21:/2"));
+        REQUIRE(l.load_asset<fake_asset, fake_nested_asset>("42:/21:/2")->content() == 2);
+
+        REQUIRE_FALSE(l.load_asset<fake_asset, binary_asset>("42:/21:/2"));
+        REQUIRE_FALSE(l.load_asset<fake_asset, fake_nested_asset>("42:/21:/none"));
+        REQUIRE_FALSE(l.load_asset<fake_asset, fake_nested_asset>("42:/21:/none:/2"));
+    }
+}
diff --git a/untests/sources/untests_high/library.cpp b/untests/sources/untests_high/library.cpp
index 04385b08..48ae5e11 100644
--- a/untests/sources/untests_high/library.cpp
+++ b/untests/sources/untests_high/library.cpp
@@ -99,25 +99,33 @@ TEST_CASE("library"){
             auto material_res = l.load_asset<material_asset>("material.json");
             REQUIRE(material_res);
 
-            auto atlas_res = l.load_asset<atlas_asset>("atlas.json");
-            REQUIRE(atlas_res);
-            REQUIRE(atlas_res->content().texture() == texture_res);
-            REQUIRE(atlas_res->content().regions().size() == 1);
-            REQUIRE(atlas_res->content().find_region("sprite"));
-            REQUIRE(atlas_res->content().find_region("sprite")->name == make_hash("sprite"));
-            REQUIRE(atlas_res->content().find_region("sprite")->pivot == v2f(1.f,2.f));
-            REQUIRE(atlas_res->content().find_region("sprite")->texrect == b2f(5.f,6.f,7.f,8.f));
-            REQUIRE_FALSE(atlas_res->content().find_region("sprite2"));
-            REQUIRE(atlas_res->content().shape_regions().size() == 1);
-            REQUIRE(atlas_res->content().find_shape_region("shape_sprite"));
-            REQUIRE(atlas_res->content().find_shape_region("shape_sprite")->name == make_hash("shape_sprite"));
-            REQUIRE(atlas_res->content().find_shape_region("shape_sprite")->pivot == v2f(3.f,4.f));
-            REQUIRE(atlas_res->content().find_shape_region("shape_sprite")->points == vector<v2f>{
-                {1.f, 2.f},
-                {3.f, 4.f},
-                {5.f, 6.f}
-            });
-            REQUIRE_FALSE(atlas_res->content().find_shape_region("shape_sprite2"));
+            {
+                auto atlas_res = l.load_asset<atlas_asset>("atlas.json");
+                REQUIRE(atlas_res);
+
+                REQUIRE(atlas_res->content().texture() == texture_res);
+                REQUIRE(atlas_res->content().regions().size() == 1);
+                REQUIRE(atlas_res->content().shape_regions().size() == 1);
+
+                const atlas::region* region = atlas_res->content().find_region("sprite");
+                REQUIRE(region);
+                REQUIRE(region->name == make_hash("sprite"));
+                REQUIRE(region->pivot == v2f(1.f,2.f));
+                REQUIRE(region->texrect == b2f(5.f,6.f,7.f,8.f));
+
+                const atlas::shape_region* shape_region = atlas_res->content().find_shape_region("shape_sprite");
+                REQUIRE(shape_region);
+                REQUIRE(shape_region->name == make_hash("shape_sprite"));
+                REQUIRE(shape_region->pivot == v2f(3.f,4.f));
+                REQUIRE(shape_region->points == vector<v2f>{
+                    {1.f, 2.f},
+                    {3.f, 4.f},
+                    {5.f, 6.f}
+                });
+
+                REQUIRE_FALSE(atlas_res->content().find_region("sprite2"));
+                REQUIRE_FALSE(atlas_res->content().find_shape_region("shape_sprite2"));
+            }
 
             {
                 auto sprite_res = l.load_asset<sprite_asset>("sprite_a.json");
diff --git a/untests/sources/untests_high/starter.cpp b/untests/sources/untests_high/starter.cpp
index 9becbba7..5143dbdb 100644
--- a/untests/sources/untests_high/starter.cpp
+++ b/untests/sources/untests_high/starter.cpp
@@ -4,8 +4,6 @@
  * Copyright (C) 2018 Matvey Cherevko
  ******************************************************************************/
 
-#include <iostream>
-
 #include "_high.hpp"
 using namespace e2d;