In Life’s Edge, Carl Zimmer explores the nature of life and investigates why scientists have struggled to draw its boundaries. He handles pythons, goes spelunking to visit hibernating bats, and even tries his hand at evolution. Zimmer visits scientists making miniature human brains to ask when life begins, and follows a voyage that delivered microscopic animals to the moon, where they now exist in a state between life and death. From the coronavirus to consciousness, Zimmer demonstrates that biology, for all its advances, has yet to achieve its greatest triumph: a full theory of life.