This work is the memoir of one of the key scientists involved in the atomic bomb and the chief research assistant and intimate friend of J. Robert Oppenheimer. A prominent member of the Manhattan Project, Robert Serber was one of a team of scientists who assembled the bombs on Tinian Island for transport to Hiroshima and Nagasaki. He was also one of the first Americans to walk among the Japanese ruins after the catastrophe. Written with science historian Robert P. Crease, this self-portrait is the story of Serber's life before, during and after World War II. It brings into focus the leading figures and events during this period in American science. Serber tells of his wartime experiences at Tinian Island and in Japan, in letters to his wife Charlotte, herself a key player at Los Alamos and the only female group leader there. These letters depict what Serber saw, such as the rows of iron office safes protruding from the rubble of Hiroshima, and the grazing horse whose hair had been scorched on one side by the fireball but was untouched on the other. Serber is also eloquent about the troubles he faced as a result of his refusal to take part in public debate about the morality of his wartime work; how his opposition to rapidly developing the hydrogen bomb earned him the enmity of Edward Teller and others; and how he was investigated and his security clearance challenged, several years before Oppenheimer's. Serber also recounts stories involving Oppenheimer, Murray Gell-Mann, Ernest O. Lawrence and Edward Teller.