Answer: Melatonin is a natural hormone that is synthesized in the human body that is responsible for controlling the sleep cycle inside the human body.
This is released when the sun sets down and there is darkness, then the level of melatonin begins to rise in the blood and its level are high till morning.
Its level is elevated in the blood for almost 12 hours and then falls back to low during daytime.
This happens in the same way daily which is controlled by a cycle and is a period event.
