# Using Physics
In order to place objects using physics you need to check Simulate Physics Toggle. Please note that a green alert will appear on the top of the Prefab Brush window when physics is running.
The Physics Menu
The Green Alert On the top of the windows.
{% hint style="info" %}
When trying to place objects without a physical collider or rigidbody, Prefab Brush will automatically add a Rigidbody and a convex MeshCollider to it. If you want more precision over your collisions, please add the colliders to it manually.
{% endhint %}
### Undo
You can also use undo when using physics
