Melatonin is an amine hormone mainly produced by the pineal gland of mammals and humans. Human pineal gland is a bean granular tissue attached to the posterior wall of the third ventricle. It has also been reported that the retina and accessory lacrimal glands of mammals can also produce a small amount of melatonin; Melatonin can also be synthesized in the eyes, brain and skin of some thermophilic animals (such as frogs) and some algae.