Niel Bohr's life spans times of revolutionary change, in science and in its impact on society. Along with Einstein, Bohr can be considered as this century's major driving force behind the new mathematical and philosophical descriptions of the atom, the nucleus, and all that resulted from them. Now available in paperback for the first time, Abraham Pais, the acclaimed biographer of Einstein, traces Bohr's progress from his well-to-do origins in late nineteenth-century Denmark to his central position in the world political scene, particularly because of the development of nuclear weapons during the Second World War. Pais describes the state of physics before Bohr and considers his legacy, both theoretical and practical. But more than this, he captures the essence of Bohr, the intensely private family man who, despite appalling personal tragedy, became one of the best-loved cultural figures of recent times.