Two decades ago Wolfram got started with cellular automata, systems of rules for whether a cell is colored black or white in a sequence down the page drawn on graph paper. With computer development by the early 1980s the "behavior" of the system could be propagated, eventually for thousands of steps, resulting in spectacular printouts Wolfram has produced with wondrous clarity. Simple rules turn out to yield great complexity, and Wolfram calls this his remarkable discovery. He creates working models of just about everything—simple cellular systems (including snowflakes), fluid flow, biological branching, embryology, pigmentation, natural selection, memory, data compression and retrieval, cryptography, markets, fundamental physics (oh yes, Wolfram picked up a Ph.D. in physics at Caltech when he was 20), space-time, manyworld cosmology, human thinking, free will, and intelligence in the universe. What starts as a purposeless recreation becomes universal in application.