Chronobiology is a relatively young science. Man's circadian clock is located in the brain and, broadly speaking, consists of bundles of nerve cells. It controls the various biorhythms of the body that even occur in every cell. The research areas of chronobiology are diverse; they are looking for answers to questions like: Do chorotypes change in the course of a lifetime? Is shift work a health hazard? Does light deficiency make you sick? What role does the circadian clock play in digestion?