The time it takes to fall asleep after taking 1 tablet of melatonin varies from person to person, and generally takes effect in about half an hour to an hour, but no generalizations can be made. Melatonin is a hormone that is produced by the pineal gland in humans and mammals as a result of an amine hormone that makes a melanin-producing cell glow, and is contained in many organisms from algae to humans. Melatonin improves sleep, shortens the light sleep stage, lengthens the deep sleep stage, reduces the number of awakenings during sleep, and lowers the wake up threshold the next morning. Since aging is closely related to free radicals, melatonin can scavenge free radicals and can slow down aging. Melatonin is synthesized in the pineal gland using tryptophan as a substrate. Melatonin secretion activity is enhanced when mammals are in the dark, and melatonin secretion stops immediately when they see light. Melatonin should not be taken as an insomnia drug, and is usually best taken once before bedtime. You should stop smoking and drinking during the medication period and avoid spicy and stimulating foods.