I don't pretend to understand much of this, but he's a key founder of chaos theory and created fractal geometry. Like I said, I don't claim to totally understand either, but I've heard of them. The Sunday Telegraph from a while back has an accessible article on the man. His Wikipedia entry, on the other hand...
NYT:
He used the geometry of fractals to explain how galaxies cluster, how wheat prices change over time and how mammalian brains fold as they grow, among other phenomena.I personally got a kick out of this paragraph from the Telegraph:
Mandelbrot was a brilliant student and held a variety of academic positions, before resigning a post in France in 1958 in order to work in IBM's famous ideas factory (a group of oddball intellectuals paid to come up with great innovations). He was already seen as a cross-disciplinarian and a maverick and had created for himself "a very hostile intellectual environment. France does not like people not to belong".
