For nearly 50 years, until his death in 1988, Richard Feynman's work lay at the heart of the development of modern physics. Always controversial, Feynman was the key physicist from his days as part of the A-bomb-making team at Los Alamos in the early 1940s, until his discovery of the reason for the Challenger space shuttle disaster 40 years later. The book combines biography with an accessible account of his thought and its context.