Today, an entomologist in a laboratory can gaze at a butterfly pupa with a microscope so powerful that the swirling cells on the pupa’s skin look like a galaxy. She can activate a single gene or knock it out. What she can’t do is discover how the insect behaves in its natural habitat—which means she doesn’t know what steps to take to preserve it from extinction, nor how any particular gene may interact with the environment. Four hundred years ago, a fifty-year-old Dutch woman set sail on a solo scientific expedition to study insect metamorphosis. She could not have imagined the routine magic that scientists perform today—but her absolute insistence on studying insects in their natural habitats was so far ahead of its time that it is only now coming back into favor. Chrysalis restores Maria Sibylla Merian to her rightful place in the history of science, taking us from golden-age Amsterdam to the Surinam tropics to modern laboratories where Merian’s insights fuel new approaches to both ecology and genetics.