Melatonin is a hormone that your brain produce that respond to darkness.

Melatonin when is produced, is secreted to the bloodstream and cerebrospinal fluid and send signal to other organs. To highest levels of melatonin secreted are during the night.

It helps with the timing of your circadian rythms.

It is connected to the time of the day, when our body is exposed to darnkenss, melatonin increases and decrease when exposed to light.

It goes through the brain to all parts of the body and its recieved by specfic receptors for melatonin.

One role of melatonin is the secretion of nocturnal melatonin that maintain sleep and control by the day and night rythm of the timing of 24 hours.

This gland is located in the center of the brain and its main function is to control the circadian cycle of sleep and wakefulness by receiving information about the state of the light and dark cycle of the environment. This information is then transmitted to produce the hormone melatonin.