melatonin

Melatonin is the body's chemical announcement of darkness, the hormone that tells your tissues night has fallen. Released by the pineal gland mainly during the hours of darkness, its rising level is a signal the brain and body read as it is night, prepare for rest. It is sometimes called the hormone of darkness rather than the hormone of sleep, because its job is to mark the time, not to force sleep directly.

Chemically melatonin is a small amine derived from serotonin, and through it from the amino acid tryptophan. Its secretion follows a sharp daily curve: nearly undetectable by day, it climbs after dusk, peaks in the middle of the night, and falls before dawn. Because bright light, especially blue-rich light, suppresses melatonin even at night, evening screen exposure can blunt the signal and delay the body's clock.

Melatonin is used as a supplement to ease jet lag and certain circadian sleep disorders, where small, well-timed doses can nudge the body clock. Honestly, its effect as a general sleeping pill is modest, and its main physiological power is as a timing signal rather than a sedative.