Metamorphism

Caterpillars represent just one stage of this transformational trek — the larval stage — during which their main purpose is to eat and grow. They grow so much during their brief lives that they typically shed their skin several times, often revamping their appearance from one instar phase to the next. Afterward, butterfly caterpillars molt one final time into a hard chrysalis to begin their magical makeover and moth caterpillars (with a few exceptions) wrap themselves in a silky cocoon.
https://www.treehugger.com/remarkable-caterpillars-and-what-they-become-4864235
Amazing world of Butterflies.