**Benoit B. Mandelbrot** is Sterling Professor of Mathematical Sciences at Yale University and a Fellow Emeritus at IBM's Thomas J. Watson Laboratory. He is the inventor of fractal geometry, whose most famous example, the Mandelbrot Set, has been replicated on millions of posters, T-shirts, and record albums. He was a leading figure in James Gleick's *Chaos* and has received the Wolf Prize in Physics, the Japan Prize in science and technology, and awards from the U.S. National Academy of Sciences, the IEEE, and numerous universities in the U.S. and abroad. His books include *Fractals: Form, Chance and Dimension*, which was later expanded into the classic *The Fractal Geometry of Nature*, which has sold more than 200,000 copies. This is his first book for lay readers on finance, a subject he has studied since the 1960s. He lives in Scarsdale, New York. **Richard L. Hudson** was the managing editor of the *Wall Street Journal's* European edition for six years, and a *Journal* reporter and editor for twenty-five years. He is a 1978 graduate of Harvard University and a 1991 Knight Fellow of MIT. He lives in Brussels, Belgium.