The document profiles 7 scientists who were key figures in the Manhattan Project: Hungarian physicist Leo Szilard conceived the idea of the nuclear chain reaction and helped initiate the project; Italian physicist Enrico Fermi demonstrated the first self-sustaining nuclear reaction; American general Leslie Groves oversaw the entire project; American physicist J. Robert Oppenheimer was the director of the Los Alamos laboratory; Hungarian-born American physicist Edward Teller developed the hydrogen bomb; German physicist Hans Bethe calculated critical mass for the weapons; and American physicist Richard Garwin worked on bomb design and later campaigned against nuclear weapons.