diff --git a/README.md b/README.md
index 95714c2..9699124 100644
--- a/README.md
+++ b/README.md
@@ -8,6 +8,20 @@ Designer-friendly Finite State Machine implemented in "Godotic" way
 > It is not recommended to be used in production yet, as api might be changed before v1.0.
 > Testing & reporting bugs are greatly appreciated.
 
+## Content
+
+- [Feature](#feature)
+- [Installation](#installation)
+- [Getting Started](#getting-started)
+  - [Editor](#editor)
+  - [Code](#code)
+- [Nested FSM](#nested-fsm)
+  - [State](#state)
+  - [Parameter](#parameter)
+- [Debug](#debug)
+- [Demo](#demo)
+- [Documentation](addons/imjp94.yafsm/README.md)
+
 ## Feature
 
 - Designer-friendly
@@ -18,6 +32,8 @@ Designer-friendly Finite State Machine implemented in "Godotic" way
   > Visualize game/UI state from flowchart
 - Zero learning curve
   > Similar workflow as using `AnimationTree`, and not required to inherit any custom class, just plug and play
+- Nested FSM
+  > Nested Finite State Machine workflow supported to create complex state machine with ease
 - Reusability
   > As a `Resource`, `StateMachine` can be used repeatedly in different scenarios(`StateMachinePlayer`) and provide different outcome based on the input.
 - Minimal
@@ -27,13 +43,13 @@ For more detail, see [CHANGELOG.md](CHANGELOG.md)
 
 ## Installation
 
-- Install directly from Godot Asset Library
+1. Install directly from Godot Asset Library
 
 or
 
-- Download this respository,
-  1. Move `addons/imjp94.yafsm` to your `{project_dir}`
-  2. Enable it from Project -> Settings -> Plugins
+1. Download this respository, move `addons/imjp94.yafsm` to your `{project_dir}`
+
+2. Enable it from Project -> Settings -> Plugins
 
 ## Getting Started
 
@@ -47,7 +63,7 @@ or
 
 3. Click on "Create StateMachine" button to get started.
 
-Finally, right-click on graph to add state node.
+Finally, `Right-Click` on graph to add state node and `Shift + Drag` on node to start connect(`Shift + Drag` again on line to reconnect)
 
 Special states:
 
@@ -64,12 +80,91 @@ After setup `StateMachine` with editor, you can connect to the following signals
 ![Signal Example](screenshots/yafsm_state_machine_player_signal_example.png)
 *Example code snippet of KinematicBody connect "updated" signal*
 
+And control `StateMachinePlayer` by accessing parameter:
+
+```gdscript
+var smp = get_node(StateMachinePlayer)
+smp.set_trigger("jump")
+smp.set_param("jump_count", 1)
+smp.get_param("on_floor", false)
+smp.has_param("velocity")
+```
+
 That's it!
 
 For most of the case, you don't have to inherit from any custom class by this plugin, simply just connect signals to your existing node and you're good to go.
 
 > See documentation below for more details
 
+## Nested FSM
+
+The only different between nested/normal FSM is how state/parameters are accessed.
+
+### State
+
+- normal state - "State"
+- nested state - "BaseState/AnotherState/EndState"
+
+```gdscript
+var normal_state = "Idle"
+var nested_state = "App/Game/Play" # EndState can be Entry/Exit
+```
+
+`StateDirectory` class is provided to traverse state path like file directory:
+
+```gdscript
+const StateDirectory = preload("addons/imjp94.yafsm/src/StateDirectory.gd)
+
+# Handle "transited" signal
+func _on_normal_state_transited(from, to):
+	match to:
+		"Entry":
+			print("Enter")
+		"Game":
+			print("Game")
+		"Exit":
+			print("Exit)
+
+# Handle "transited" signal
+func _on_nested_state_transited(from, to):
+	var to_dir = StateDirectory.new(to)
+
+	match to_dir.next(): # Initial next() required to move to base state
+		"Entry":
+			print("Enter")
+		"Game":
+			match to_dir.next(): # It can be called recursively, until return null
+				"Entry":
+					print("Game Enter") # Game/Entry
+		"Exit":
+			print("Exit)
+```
+
+### Parameter
+
+Behind the scene, `StateMachinePlayer` always differentiate parameters into 2 types: global & local
+
+- global parameter
+  - Just a normal parameter - "param_name"
+  - Never erased automatically, unless `erase_param`/`clear_param` called by user
+- local parameter 
+  - Parameter that local to nested state - "BaseState/TargetState/param_name"
+  - Erased upon Exit, for example, "App/Game/Exit" will cause all local parameter("App/Game/{param_name}") to be erased
+
+```gdscript
+var smp = get_node(StateMachinePlayer)
+var global_param = smp.get_param("state")
+var local_param = smp.get_param("App/Game/playing")
+```
+
+Besides of controlling `StateMachinePlayer`, it's useful to set arbitrary value with `set_param`
+
+```gdscript
+var smp = get_node(StateMachinePlayer)
+smp.set_param("game", preload("game.scn"))
+var game_scn = smp.get_param("game")
+```
+
 ### Debug
 
 - Stack
@@ -77,7 +172,7 @@ For most of the case, you don't have to inherit from any custom class by this pl
   
 ## Demo
 
-Check out [gd-YAFSM-demo](https://github.com/imjp94/gd-yafsm-demo) for how you can integrate gd-YAFSM into you project.
+Check out [gd-YAFSM-demo](https://github.com/imjp94/gd-yafsm-demo) for how you can integrate gd-YAFSM into you project and manage app state with `StateMachine`
 
 ## Documentation
 
diff --git a/addons/imjp94.yafsm/README.md b/addons/imjp94.yafsm/README.md
index eace719..f1b6db0 100644
--- a/addons/imjp94.yafsm/README.md
+++ b/addons/imjp94.yafsm/README.md
@@ -2,7 +2,7 @@
 
 ## Classes
 
-All of the classes are located in `res://addons/imjp94.yafsm/src` but you can just preload `res://addons/imjp94.yafsm/YAFSM.gd` to import all classes available:
+All of the class are located in `res://addons/imjp94.yafsm/src` but you can just preload `res://addons/imjp94.yafsm/YAFSM.gd` to import all class available:
 
 ```gdscript
 const YAFSM = preload("res://addons/imjp94.yafsm/YAFSM.gd")
@@ -29,8 +29,8 @@ const State = YAFSM.State
   - `process_mode # ProcessMode of player`
   - signals:
     - `transited(from, to) # Transition of state`
-    - `entered() # Entry of state machine`
-    - `exited() # Exit of state machine`
+    - `entered(to) # Entry of state machine(including nested), empty string equals to root`
+    - `exited(from) # Exit of state machine(including nested, empty string equals to root`
     - `updated(state, delta) # Time to update(based on process_mode), up to user to handle any logic, for example, update movement of KinematicBody`
 
 ### Control
@@ -38,6 +38,11 @@ const State = YAFSM.State
 - [StackPlayerDebugger](src/debugger/StackPlayerDebugger.gd)
   > Visualize stack of parent StackPlayer on screen
 
+### Reference
+
+- [StateDirectory](src/StateDirectory.gd)
+  > Convert state path to directory object for traversal, mainly used for nested state
+
 ### Resource
 
 Relationship between all `Resource`s can be best represented as below:
@@ -73,3 +78,4 @@ var condition = transition.conditions[condition_name] # keyed by condition name
 - [BooleanCondition](src/conditions/BooleanCondition.gd)(`extends ValueCondition`)
 - [IntegerCondition](src/conditions/IntegerCondition.gd)(`extends ValueCondition`)
 - [FloatCondition](src/conditions/FloatCondition.gd)(`extends ValueCondition`)
+- [StringCondition](src/conditions/StringCondition.gd)(`extends ValueCondition`)
diff --git a/screenshots/yafsm_editor_showcase.gif b/screenshots/yafsm_editor_showcase.gif
index b23411a..7bfbb60 100644
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