Complexity theory is one of the most controversial areas of current scientific research. Developing out of chaos theory, complexity suggests that there are hidden tendencies in nature to select ordered states, even when statistically they are vastly outnumbered by chaotic possibilities: that there is a deep natural impulse towards order, counteracting the degenerative tendencies of the Second Law of Thermodynamics. Like chaos, complexity is a multidisciplinary area of research and those involved include physicists, economists and biologists.