Melatonin is a hormone produced by a gland in the brain. The secretion of melatonin is inhibited in the presence of light and stimulated when it is dark. By secreting melatonin, this hormone "says" to the brain that it is dark and that it is the right time to sleep. Changes in the rhythm of life (night work) or the misuse of screens can disrupt the secretion of melatonin and thus impair sleep. Taking melatonin as a dietary supplement can restore a normal rate and facilitate falling asleep.