To become a butterfly, a caterpillar first digests itself. But certain groups of cells survive, turning the soup into eyes, wings, antennae and other adult structures.

As children, many of us learn about the wondrous process by which a caterpillar morphs into a butterfly. The story usually begins with a very hungry caterpillar hatching from an egg. The caterpillar, or what is more scientifically termed a larva, stuffs itself with leaves, growing plumper and longer through a series of molts in which it sheds its skin. One day, the caterpillar stops eating, hangs upside down from a twig or leaf and spins itself a silky cocoon or molts into a shiny chrysalis. Within its protective casing, the caterpillar radically transforms its body, eventually emerging as a butterfly or moth.

But what does that radical transformation entail? How does a caterpillar rearrange itself into a butterfly? What happens inside a chrysalis or cocoon?

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