The quantum entered physics with a jolt. It didn't fit anywhere; it made no sense; it contradicted everything we thought we knew about nature. Yet the data seemed to demand it. ... The story of Werner Heisenberg and his science is the story of the desperate failures and ultimate triumphs of the small band of brilliant physicists who-during an incredibly intense period of struggle with the data, the theories, and each other during the 1920s-brought about a revolutionary new understanding of the atomic world known as quantum mechanics.