grandchild of an object not showing in prefab after apply

I have some gamobject 0 with a child gameobject 1. 1 has gameobject child 2. I hit apply on gameobject 0 to apply the change to prefab. But in the prefab, there is 1 but not showing it’s childern 2. I also tried hit apply on gameobject 1 (which is child of 0), nothing worked out. Any ideas?

Thanks in advance.

Prefabs in the Assets folder only show the children, not any deeper than that. If you drag the prefab back into the scene to create a new gameobject, you’ll see the rest of it still exists.