Metamorphosis is a biological process by which an animal physically develops after birth or hatching. It involves a conspicuous and relatively abrupt change in the animal's body structure through cell growth and differentiation. Some animals undergo metamorphosis, while others do not. Those that do are said to be holometabolous, while those that do not are said to be ametabolous or hemimetabolous.
The most common example of metamorphosis is the transformation of a caterpillar into a butterfly or moth. During this process, the caterpillar's body breaks down and reassembles itself into a completely different form, complete with wings and a proboscis. Other animals that undergo metamorphosis include frogs, salamanders, and some fish.
Metamorphosis is a complex process that is controlled by hormones. It is thought to have evolved as a way for animals to adapt to different environments. For example, the caterpillar stage of a butterfly is well-suited for eating leaves, while the adult butterfly is better suited for flying and reproducing.