Although scientists are unsure exactly why we sleep, there are many clues about the functions that sleep serves and how getting more and higher quality sleep can improve our health and wellbeing. Sleep is a physical and mental resting state in which a person becomes relatively inactive and unaware of the environment.

Although a sleeping person may appear inactive, some functions of the brain and body are actually more active during sleep than when we're awake. Many physiological variables are controlled during wakefulness at levels that are optimal for the body's functioning. Our temperature, blood pressure, and levels of oxygen, carbon dioxide, and glucose in the blood remain quite constant during wakefulness. During sleep, however, physiological demands are reduced and temperature and blood pressure drop.

For centuries, physicians believed that sleep was a period of brain inactivity, yet research over the last 60 years has shown us that the brain remains active during sleep.
Human being bodies regulate sleep in much the same way that they regulate eating, drinking, and breathing. This suggests that sleep serves a similar critical role in people health and well-being.

Sleep plays an important role in memory, both before and after learning a new task. First, a sleep-deprived person cannot focus attention optimally and therefore cannot learn efficiently. Second, a sleep itself has a role in the consolidation of memory, which is essential for learning new information.