General:
* Transformation
* Change
* Development
* Evolution
* Alteration
* Transition
* Remaking
Specific to biological contexts:
* For insects: Molt, pupation, chrysalis
* For other animals: Metamorphosis (sometimes used for other animals with significant changes), development, growth
For figurative contexts:
* Reinvention
* Makeover
* Revival
* Rebirth
* Resurrection
The best synonym will depend on the specific meaning you are trying to convey.