"Dynamical systems theory began in the late nineteenth century with the work of Henri Poincaré (1854–1912). He solved an important problem in celestial mechanics by using techniques of dynamical systems. In modern times, Stephen Smale, Adrien Douady, John Milnor, Lennart Carleson, and many other notable mathematicians have helped to develop this theory into a powerful mathematical tool. The subject is exciting in that it integrates analysis, geometry, and computer graphics into a whole that is greater than the sum of its parts."