Transhumanism is a movement pushing the limits of our biology—of our senses, intelligence, and lifespans—with technology. Its supporters have reached a critical mass and now include some of the biggest names in Silicon Valley and beyond, among them Peter Thiel, Elon Musk, and Ray Kurzweil. In this provocative and eye-opening account, journalist Mark O’Connell explores the staggering (and terrifying) possibilities that present themselves when you think of your body as an outmoded device. He visits the world’s foremost cryonics facility to witness how some have chosen to forestall death, discovers an underground collective of biohackers boosting their senses by implanting electronics under their skin, and meets with members of a team urgently investigating how to protect mankind from rogue artificial superintelligence. In investigating what it means to be a machine, O’Connell shines a light on our ancient desire to transcend the animal condition—and offers a surprising meditation on what it means to be human.