The cellular circadian oscillator -A fundamental biological mechanism corresponding to a geophysical periodicity.

In correspondence to the geophysical cycle of the solar day, the majority of eucaryotic organisms exhibit the phenomenon of circadian periodicity. This type of biological rhythm is reviewed, mainly as cytological aspects, with regard to the temporal organization of the eucaryote, the question of endogeneity, the occurrence in cells of multicellular organisms, and attempts to explain the molecular mechanism of the basic oscillator. [ABSTRACT FROM AUTHOR]