diff --git a/.gitignore b/.gitignore
index 34d64bd..3a4254f 100644
--- a/.gitignore
+++ b/.gitignore
@@ -2,7 +2,6 @@
 !*/
 !source/**
 !tests/**
-
 !README.md
 !dub.json
 !.gitignore
\ No newline at end of file
diff --git a/source/ecs/entity.d b/source/ecs/entity.d
index 3757d80..931dfa0 100644
--- a/source/ecs/entity.d
+++ b/source/ecs/entity.d
@@ -1,3 +1,6 @@
+/************************************************************************************************************************
+*Entity module.
+*/
 module ecs.entity;
 
 import ecs.manager;
diff --git a/source/ecs/manager.d b/source/ecs/manager.d
index aa8c20a..87491ea 100644
--- a/source/ecs/manager.d
+++ b/source/ecs/manager.d
@@ -1,3 +1,6 @@
+/************************************************************************************************************************
+*Most important module.
+*/
 module ecs.manager;
 
 import std.algorithm : max;
@@ -24,6 +27,9 @@ alias gEntityManager = EntityManager.instance;
 alias gEventManager = EntityManager.instance;
 alias SerializeVector = ecs.vector.Vector!ubyte;
 
+/************************************************************************************************************************
+*Entity manager is responsible for everything.
+*/
 class EntityManager
 {
     export static void initialize(uint threads_count)
@@ -189,8 +195,9 @@ class EntityManager
     *Systems can be registered from external dynamic library, and can be registered after adding entities too.
     *System mustn't be registered before components which system want to use, in this case functions call assertion.
     *
-    *params:
-    *priority = system priority. Priority determines order of execution of systems updates.
+    *Params:
+    *priority = system priority. Priority determines order of execution of systems updates
+    *pass = index of UpdatePass which sholud call system update
     */
     void registerSystem(Sys)(int priority, ushort pass = 0)
     {
@@ -730,11 +737,17 @@ class EntityManager
         Sys.system_id = system.id;
     }
 
+    /************************************************************************************************************************
+    *Return system ECS api by id
+    */
     System* getSystem(ushort id) nothrow @nogc
     {
         return &systems[id];
     }
 
+    /************************************************************************************************************************
+    *Return pointer to system registered in manager
+    */
     Sys* getSystem(Sys)() nothrow @nogc
     {
         return cast(Sys*) systems[Sys.system_id].m_system_pointer;
@@ -766,7 +779,6 @@ class EntityManager
                 && Parameters!(Comp.onDestroy).length == 0)
         {
             static void callDestroy(void* pointer) nothrow @nogc
-            
             {
                 (cast(void delegate() nothrow @nogc)&(cast(Comp*) pointer).onDestroy)();
             }
@@ -774,6 +786,18 @@ class EntityManager
             info.destroy_callback = &callDestroy;
         }
 
+        static if (hasMember!(Comp, "onCreate") && isFunction!(Comp.onCreate)
+                && is(ReturnType!(Comp.onCreate) == void)
+                && Parameters!(Comp.onCreate).length == 0)
+        {
+            static void callCreate(void* pointer) nothrow @nogc
+            {
+                (cast(void delegate() nothrow @nogc)&(cast(Comp*) pointer).onCreate)();
+            }
+
+            info.create_callback = &callCreate;
+        }
+
         info.size = Comp.sizeof;
         info.alignment = Comp.alignof; //8;
         info.init_data = Mallocator.instance.makeArray!ubyte(Comp.sizeof);
@@ -1025,7 +1049,7 @@ class EntityManager
     /************************************************************************************************************************
     *Allocate EntityTemplate with specifed components and returns pointer to it.
     *
-    *params:
+    *Params:
     *components_ids = array of components allocated with template
     */
     export EntityTemplate* allocateTemplate(ushort[] components_ids)
@@ -1069,7 +1093,7 @@ class EntityManager
     /************************************************************************************************************************
     *Returns entity type info.
     *
-    *params:
+    *Params:
     *ids = array of components
     */
     export EntityInfo* getEntityInfo(ushort[] ids)
@@ -1174,7 +1198,7 @@ class EntityManager
     /************************************************************************************************************************
     *Returns pointer to entity.
     *
-    *params:
+    *Params:
     *id = ID of entity
     */
     export Entity* getEntity(EntityID id) nothrow @nogc
@@ -1185,7 +1209,7 @@ class EntityManager
     /************************************************************************************************************************
     *Remove components from entity by IDs. Components will be removed on end of frame.
     *
-    *params:
+    *Params:
     *entity_id = ID of entity
     *del_ids = array of components IDs
     */
@@ -1262,8 +1286,8 @@ class EntityManager
     /************************************************************************************************************************
     *Remove coponents from entity.
     *
-    *params:
-    *Compoenents = components types to remove
+    *Params:
+    *Components = components types to remove
     *entity_id = ID of entity
     */
     void removeComponents(Components...)(EntityID entity_id)
@@ -1411,9 +1435,9 @@ class EntityManager
     /************************************************************************************************************************
     *Add components to entity. Components will be added on end of frame.
     *
-    *params:
+    *Params:
     *entity_id = ID of entity to remove
-    *tmpl = pointer entity template allocated by EntityManager.
+    *comps = components to add
     */
     void addComponents(Components...)(const EntityID entity_id, Components comps) nothrow @nogc
     {
@@ -1452,8 +1476,8 @@ class EntityManager
     /************************************************************************************************************************
     *Free template memory.
     *
-    *params:
-    *tmpl = pointer entity template allocated by EntityManager.
+    *Params:
+    *template_ = pointer entity template allocated by EntityManager.
     */
     export void freeTemplate(EntityTemplate* template_)
     {
@@ -1464,7 +1488,7 @@ class EntityManager
     /************************************************************************************************************************
     *Add entity to system.
     *
-    *params:
+    *Params:
     *tmpl = pointer entity template allocated by EntityManager.
     */
     export ref Entity addEntity(EntityTemplate* tmpl)
@@ -1489,6 +1513,13 @@ class EntityManager
         {
             memcpy(cast(void*) block + info.deltas[comp] + components[comp].size * id,
                     tmpl.entity_data.ptr + info.tmpl_deltas[comp], components[comp].size);
+
+            if (components[comp].create_callback)
+            {
+                components[comp].create_callback(cast(
+                        void*) block + info.deltas[comp] + id * components[comp].size);
+            }
+
         }
 
         if (index == 1)
@@ -1578,7 +1609,7 @@ class EntityManager
     /************************************************************************************************************************
     *Remove entity by ID. Entity will be removed on frame end.
     *
-    *params:
+    *Params:
     *id = id of entity to remove
     */
     export void removeEntity(EntityID id)
@@ -1660,7 +1691,7 @@ class EntityManager
     /************************************************************************************************************************
     *functions return MetaData of page.
     *
-    *params:
+    *Params:
     *pointer = pointer to any data of entity (i.e. component data pointer)
     */
     export EntitiesBlock* getMetaData(const void* pointer) nothrow @nogc
@@ -1983,6 +2014,8 @@ class EntityManager
         ubyte[] init_data;
         ///Pointer to component destroy callback
         void function(void* pointer) nothrow @nogc destroy_callback;
+        ///Pointer to component create callback
+        void function(void* pointer) nothrow @nogc create_callback;
     }
 
     struct EventCaller
diff --git a/source/ecs/system.d b/source/ecs/system.d
index d21e75a..ba2168e 100644
--- a/source/ecs/system.d
+++ b/source/ecs/system.d
@@ -1,3 +1,6 @@
+/************************************************************************************************************************
+*System module.
+*/
 module ecs.system;
 
 import ecs.entity;
@@ -5,6 +8,13 @@ import ecs.manager;
 
 /************************************************************************************************************************
 *System contain data required to proper glue EntityManager with Systems.
+*System callbacks:
+*<br/>-void onEnable()
+*<br/>-void onDisable();
+*<br/>-bool onBegin();
+*<br/>-void onEnd();
+*<br/>-void onCreate()
+*<br/>-void onDestroy();
 */
 struct System
 {