In 'Life's Edge: The Search for What It Means to Be Alive,' celebrated science writer Carl Zimmer takes readers on a journey to explore one of humanity’s most profound questions: What is life? Zimmer delves into the challenges scientists face as they attempt to define life—an endeavor that grows more complex the deeper they probe into the living world. From the nuances of protocells to the complexities of human brains, and from the earliest zygotes to the behavior of pandemic viruses, Zimmer uncovers the countless attempts to pinpoint where life begins and ends. He examines how life’s definition becomes crucial in debates over controversial issues like abortion and end-of-life decisions. With accounts of peculiar experiments, including his own efforts to evolve life in a test tube, Zimmer navigates readers through a myriad of definitions and the intricate experiments behind them. Whether encountering pythons or bats, revisiting Dr. Frankenstein's monster, or revealing attempts to engineer life anew, Zimmer's narrative captures the essence of the elusive boundary of existence and the remarkable discoveries on the edge of life itself.