Melatonin is a natural hormone that your brain produces in response to darkness and plays an important role in wake and sleep orders. It is released in the reaction of darkness and obscured by light. As the evening begins after sunset, the pineal gland starts to emit Melatonin. As the level of melatonin increases, you feel less active and feel sleepy. Once you feel that melatonin hormones are not produced as much as required to get sound sleep.