Nature's Harmony Melatonin - 3 mg - Bonus Size - Melatonin is a hormone produced by the pineal gland in the brain. Once In the natural sleep-wake cycle, darkness triggers the release of melatonin. Once released into the bloodstream, melatonin prepares the body for sleep, decreasing temperature, alertness and performance. Melatonin supplements interact with melatonin receptors in the brain in the same way to induce sleep and help regulate the body’s normal sleep patterns.