Es ist ein Licht, das in meinem Mund erlöscht.

Georg Trakl, De profoundis, in: Das wilde Herz, Gedichte

Circadian Rhythms are to be found in every cell in the living world. This complex system can be seen as the default setting that gives structure, not only to cycles of sleep and human waking hours but also patterns of the daily life cycle of animals, plants, and fungi. It is the so-called body clock that makes a plant open and closes its flowers in a dark wardrobe. The term describes a complex system of intertwined biological processes which act like a metronome to regulate the rhythms of overlaid functions within each cell. These rhythms are working on different levels from the bio-molecular cellular level all the way up to the behavioral. Outside stimuli such as artificial light and the deprivation of sleep and nutrition disrupt this fine framework. Circadian rhythms are the underlying mechanisms that are responsible for cell regeneration and also memory. In the dark, the body clock ensures the regular function of the cell and prepares the organism for the next day.