To stay healthy is a good night's sleep is a prerequisite.
The body gets the time to recover from the physical and mental effort, gained during the day. One speaks of a normal circadian rhythm (day wake up and sleep at night).
This rhythm is controlled by the body (biological clock) because the pineal gland releases melatonin, the endogenous substance that makes for a good night's sleep. The normal circadian rhythm can be broken by eg shift work or jet lag. As a result, the body may require additional support. Melatonin Sleep provides support in these situations.