Metamorphosis.

met·a·mor·pho·sis [met-uh-mawr-fuh-sis]
–noun, plural -ses [-seez]
Pronunciation.
1. Biology. a profound change in form from one stage to the next in the life history of an organism, as from the caterpillar to the pupa and from the pupa to the adult butterfly.
2. a complete change of form, structure, or substance, as transformation by magic or witchcraft.
3. any complete change in appearance, character, circumstances, etc.
4. a form resulting from any such change.