find child of gameobject unity

gameObject.transform.Find("ChildGameObject").gameObject;

//This insures that you are finding the child instead of finding another
//GameObject's Child.

//Instantiate Prefab
GameObject originalGameObject  = Instantiate(prefab);

//To find `child1` which is the first index(0)
GameObject child2 = originalGameObject.transform.GetChild(0).gameObject;

//To find `child2` which is the second index(1)
GameObject child2 = originalGameObject.transform.GetChild(1).gameObject;

//To find `child3` which is the third index(2)
GameObject child3 = originalGameObject.transform.GetChild(2).gameObject;

Gameobject.Find("ChildName") ;