Although the World War II efforts to develop nuclear weapons have inspired a very large literature, it struck us as noteworthy that virtually nothing existed in the form of firsthand accounts. Now It Can Be Told, by General Leslie Groves, the Manhattan Project's military commander, is probably the most prominent exception, but the scientists themselves seem to have shown little interest in publishing their reminiscences. Believing that it would be not only worthwhile for posterity, but ex tremely interesting for the present generation to hear about the aspirations, fears, and activities of those who participated in this watershed of science and government collaboration, we arranged the public lecture series repre sented by this book.! We chose to focus upon Los Alamos since the project's efforts culminated there. The isolated laboratory in New Mexico was created to design and construct the first atomic bombs. More scientific brainpower was accumulated there than at any time since Isaac Newton dined alone, and the interactions with this community are of sociological interest, as the results of their work are of political import.