Melatonin is a hormone your brain produces in response to darkness. It is produced by the pineal gland in the brain but also found in other areas, such as the eyes, bone marrow and gut. It helps with the timing of your circadian rhythms (24-hour internal clock) and with sleep. Melatonin itself won’t knock you out, it simply lets your body know it’s night-time so you can relax and fall asleep easier. Melatonin also helps regulate your body temperature, blood pressure and hormone levels.