How did an obscure academic idea pave the way to the Holocaust within just fifty years? Why does eugenics still loom large in the 21st century, despite its genocidal past? Did eugenics work? Could it work? Or was it always a pseudoscientific fantasy? Throughout history, people have sought to reduce suffering, eliminate disease and enhance desirable qualities in their children. In the Victorian era eugenics, a full-blooded attempt to impose control over unruly biology, began to grow among the powerful and quickly spread to dozens of countries around the world. But these ideas are not merely historical: today, with new gene editing techniques, conversations are happening about tinkering with the DNA of our unborn children to make them smarter, fitter, stronger. Deeply steeped in contemporary genetics, CONTROL offers a vital account of one of the defining - and most destructive - ideas of the twentieth century.