Henri Poincare (1854-1912), French mathematician. Poincare is considered one of the greatest mathematicians of all time. He worked on celestial mechanics, topology, relativity and is considered the founder of chaos theory. The spheres, knots and surfaces around his head relate to his work. He also posed the Poincare Conjecture, in 1904, a problem in topology that remained unsolved for nearly a century, although a proof by Grigori Perelman in 2003 is generally considered correct.