Chaos lurks on the border between regularity and randomness. While it masquerades as randomness, chaos is in reality a deterministic phenomenon. When we see irregularity, our thoughts hasten to blame randomness and disorder. Why should this be so? How can anything as marvellously ordered as the human body be dependent on processes that are completely random? Why is it that when the ubiquitous irregularity of biological systems is studied, instant conclusions are drawn about randomness? Recently we have begun to realize that irregularity is much richer than mere randomness can encompass. Thus we are brought to chaos.