Abstract
Circadian rhythms are virtually ubiquitous in eukaryotes and have been shown to exist even in some prokaryotes. The generally accepted view is that these rhythms are generated by an endogenous clock. Recent progress, especially in the Drosophila, Neurospora and mouse systems, has revealed new clock components and mechanisms. These include the mouse clock gene, the Drosophila timeless gene, and the role of light in Neurospora.
