Hormone secreted by Pineal gland which exerts its function by regulating the Circadian pattern of sleeping. It is naturally found in the mother's milk. The level of Melatonin in the plasma and breast milk increases by night. It is believed that helps to organize the sleep - awake cycle in breastfed newborns and infants. It has antioxidant and anti-inflammatory properties, and, it is found in many foods, either vegetable or animal in origin (meat, fish), eggs, wine and beer. On latest update, no relevant published data related to breastfeeding were found, however, known side-effects are mild and few. It is being used for co-treatment of several conditions in newborn infants and prematures, with good tolerance in spite of higher doses than those excreted in the breast milk.