The study of complex adaptive systems, a subset of nonlinear dynamical systems, has recently become a major focus of interdisciplinary research in the social and natural sciences. Nonlinear systems are ubiquitous; as mathematician Stanislaw Ulam observed, to speak of “nonlinear science” is like calling zoology the study of “nonelephant animals”. The initial phase of research on nonlinear systems focused on deterministic chaos, but more recent studies have investigated the properties of self-organizing systems or anti-chaos. For mathematicians and physicists, the biggest surprise is that complexity lurks within extremely simple systems. For biologists, it is the idea that natural selection is not the sole source of order in the biological world. In the social sciences, it is suggested that emergence – the idea that complex global patterns with new properties can emerge from local interactions – could have a comparable impact.