"How many creatures walking on this earth / Have their first being in another form?" the Roman poet Ovid asked two thousand years ago. He could not have known the full extent of the truth: today, biologists estimate a stunning three-quarters of all animal species on Earth undergo some form of metamorphosis.

But why do tadpoles transform into frogs, caterpillars into butterflies, elvers into eels, immortal jellyfish from sea sprigs to medusae and back again, growing younger and younger in frigid ocean depths? Why must creatures go through massive destruction and remodeling to become who they are? Tracing a path from Aristotle to Darwin to cutting-edge science today, Harman explores that central mystery.

Metamorphosis, however, isn't just a biological puzzle: it takes us to the very heart of questions of being and identity, whatever kind of change we humans may undergo. Metamorphosis is a new classic of natural history: a book that, by unveiling a mystery of nature, causes us to relearn ourselves.