This official NASA history chronicles the behind-the-scenes conflicts and cooperation during the Apollo expeditions. It shows how the space agency's scientists, who were primarily interested in the Moon itself, worked out their differences with the engineers, who were charged with the astronauts' safe landing and return. The close collaboration between the scientists and engineers ensured the success of a program that remains a major achievement for both fields. The first half of the book concerns the preparations for the Moon landings, tracing the development of the Apollo science program from the earliest days. The second half documents the flights that followed Apollo 11, during which twelve astronauts explored the lunar surface and returned with samples for investigation. The author drew upon the Lyndon B. Johnson Space Center's collection of more than 31,000 Apollo-related documents and conducted more than 300 interviews with program participants to assemble this definitive survey.