Cryptochromes (from the Greek κρυπτός χρώμα, "hidden colour") are a class of flavoproteins that are sensitive to blue light. They are found in plants and animals. Cryptochromes are involved in the circadian rhythms of plants and animals, and in the sensing of magnetic fields in a number of species. The name cryptochrome was proposed as a portmanteau combining the cryptic nature of the photoreceptor, and the cryptogamic organisms on which many blue-light studies were carried out.