The details of entering Play Mode

With SceneA Scene contains the environments and menus of your game. Think of each unique Scene file as a unique level. In each Scene, you place your environments, obstacles, and decorations, essentially designing and building your game in pieces. More info
See in Glossary Reloading and Domain Reloading enabled, this is the full list of all processes and events that Unity performs when entering Play Mode:

1. The AssemblyReloadEvent beforeAssemblyReload event is raised.
2. The C# domain is stopped:
   a. OnDisable() is called for all ScriptableObjects and MonoBehaviours.
   b. Unity waits for all async operations to finish.
3. The state of all MonoBehaviours and ScriptableObjects is serialized.
   a. OnBeforeSerialize() is called.
   b. All public and private field values are serialized, except those marked with [NonSerialized].
4. Managed wrappers are disconnected from native Unity objects.
5. The Unity Child Domain is reloaded:
   a. Mono domain unload:
   i. The AppDomain.DomainUnload event is raised.
   ii. The Unity Child Domain is destroyed
   1. GC and finalizers are called.
   2. Threads are terminated.
   3. All JIT info is deleted.
   b. The new Unity Child Domain is created.
6. The assemblies are loaded:
   a. System assemblies are loaded.
   b. Unity assemblies are loaded.
   c. User assemblies are loaded.
7. The synchronization context is initialized.
8. The scripting state is restored.
   a. The scriptable part of all Unity objects is recreated.
   i. Constructors are called, and statics are assigned their default values.
   b. The state of all Unity objects is deserialized:
   i. The serialized stated of all Unity objects are restored.
   1. The OnAfterDeserialize event is raised.
   ii. OnValidate() is called.
   iii. For scriptsA piece of code that allows you to create your own Components, trigger game events, modify Component properties over time and respond to user input in any way you like. More info
   See in Glossary using the [ExecuteInEditMode] attribute:
   1. OnEnable() is called.
   2. OnDisable() is called.
   3. OnDestroy() is called.
9. Methods with the InitializeOnLoad and InitializeOnLoadMethod are called.
10. The AssemblyReloadEvent afterAssemblyReload is called.