Melatonin is mostly known for its ability to induce sleep. Melatonin is produced by the pineal gland. It shortens the time it takes to fall asleep but it doesn’t impact deep sleep or REM phases of sleep. In saying this, it does cause relaxation of muscles and nerves which does make sleep better. The highest levels of melatonin production are at night. Darkness of a night and exposure to strong morning sunlight help the optimal production of melatonin.