Cryptochromes are flavin-containing blue light photoreceptors related to photolyases - they are found in both plants and animals and have recently been described for bacteria. In plants, cryptochromes perform a variety of functions including the entrainment of circadian rhythms. They serve a similar role in Drosophila and mammals, where the cryptochromes also perform an additional function as an essential component of the circadian clock.
Cashmore, A. R. (2003, September 5). Cryptochromes: Enabling plants and animals to determine circadian time. Cell. Cell Press. https://doi.org/10.1016/j.cell.2003.08.004