Mathematician Henri Poincare? was boarding a bus when he realized that the transformations of non-Euclidean geometry were just those he needed in his research on the theory of functions. He did not have to interrupt his conversation, still less to verify the equation in detail; his insight was complete at that point. Poincare?'s insight into his own creativity -- his awareness that preliminary cogitation and the working of the subconscious had prepared his mind for an intuitive flash of recognition -- is just one of many possible analyses of scientific creativity, a subject as fascinating as it is elusive. The authors of this book have chosen to search for the springs of scientific creativity by examining the lives and work of a dozen innovative thinkers in the fields of mathematics, physics, and chemistry from the seventeenth down to the mid-twentieth century.