Rama · CC BY-SA 2.0 fr

A mathematician who gave a name and a rigorous framework to a kind of complexity that classical geometry couldn't describe — the rough, self-repeating shapes of coastlines, clouds, and mountain ranges — coining the word "fractal" for it. Working at IBM, he used the company's computers to render these structures visually, leading to his 1979-80 discovery of the Mandelbrot set, whose image later became one of the most recognizable in mathematics. He also applied the same statistical thinking to cotton futures and financial markets, arguing decades before the 2008 crisis that conventional models badly underestimated the likelihood of extreme events.