This is a behind-the-scenes account of the invention of one of the most significant biotechnological discoveries in our time - the polymerase chain reaction. Transforming the practice and potential of molecular biology, PCR extends scientists' ability to identify and manipulate genetic materials and accurately reproduces millions of copies of a given segment in a short period of time. It makes abundant what was once scarce - the genetic material required for experimentation. This study explores the culture of biotechnology as it emerged at Cetus Corporation during the 1980s and focuses on its distinctive configuration of scientific, technical, social, economic, political, and legal elements, each of which had its own separate trajectory over the preceding decade. The book contains interviews with the cast of characters who made PCR, including Kary Mullin, the maverick who received the Nobel prize for "discovering" it, as well as the team of young scientists and the company's business leaders. This book shows how a contingently-assembled practice emerged, composed of distinctive subjects, the site where they worked, and the object they invented.