The body is the most complex machine in the world, and the only one for which you cannot get a replacement part from the manufacturer. For centuries, medicine has reached for what’s available―sculpting noses from brass, borrowing skin from frogs and hearts from pigs, crafting eye parts from jet canopies and breasts from petroleum by-products. Today we’re attempting to grow body parts from scratch using stem cells and 3D printers. How are we doing? Are we there yet?

In Replaceable You, Mary Roach explores the remarkable advances and difficult questions prompted by the human body’s failings. When and how does a person decide they’d be better off with a prosthetic than their existing limb? Can a donated heart be made to beat forever? Can an intestine provide a workable substitute for a vagina?

Roach dives in with her characteristic verve and infectious wit. Her travels take her to the OR at a legendary burn unit in Boston, a “superclean” xeno-pigsty in China, and a stem cell “hair nursery” in the San Diego tech hub. She talks with researchers and surgeons, amputees and ostomates, printers of kidneys and designers of wearable organs. She spends time in a working iron lung from the 1950s, stays up all night with recovery techs as they disassemble and reassemble a tissue donor, and travels across Mongolia with the cataract surgeons of Orbis International.