Cryptochrome is a blue/ultraviolet-A (UV-A) light receptor found in a wide range of organisms from bateria to humans. It was so named because the early studies of cryptochromes were largely done in cryptogamic (flowerless) plants, and because its molecular nature once remained cryptic. Cryptochromes are the only type of photoreceptor known to function in both the plant and animal kingdoms, mediating the influence of light on plant development and the biological clock in plants and animals. Cryptochromes are flavoproteins that share structural similarities with the photoactive deoxyribonucleic acid (DNA)–repairing enzyme DNA photolyase, but do not have photolyase activity.