For most people, a good night’s sleep seems like an innocuous goal. But scientists spend much of their waking hours trying to understand how this essential activity impacts the brain and body. The results are fascinating and often surprising.

Before the 1950s, many thought that sleep was a passive state during which the brain and body were dormant. Now, we know that the brain and body are engaged in important processes that help them prepare for the day ahead and recover from events that happened during the waking period. Those processes include helping the brain lock memories into long-term memory and erasing the useless information that might otherwise clutter the nervous system. They also play a key role in the regulation of emotions. Getting enough sleep helps the body repair muscle tissue, which is why athletes need to get plenty of rest to recover from a hard workout. And a good night’s sleep helps the body to fight off infection. During slumber, the body produces cytokines, proteins that direct immune cells to attack germs and other harmful agents.

Getting enough sleep is also essential for your mental health. During slumber, your brain works to consolidate new memories and helps you control emotions. It’s why you are likely to feel irritable and moody after an inadequate night of sleep. The glymphatic system, which clears waste from your central nervous system, is also activated during sleep to eliminate the buildup of toxic byproducts that accumulate throughout the day.

Studies also show that adequate sleep helps you maintain a healthy weight and reduces the risk of heart disease. In fact, the American Heart Association lists sleep as one of its “Life’s Simple 7,” along with physical activity, a healthy diet, moderate alcohol consumption and non-smoking.

While some researchers have used subjective criteria such as the sensation of a state of “below consciousness” to identify states as being sleep, others have relied on electrophysiological measurements to define sleep. For example, a recurring pattern of EEG brain waves and decreased critical reactivity has led to the unequivocal designation of sleep for most mammals, birds and some reptiles. In contrast, similar EEG patterns have not been observed in fish and insects.

Getting enough sleep may be as easy as making it a priority and creating a calming sleep environment. For instance, make sure your bedroom is dark and quiet. Put a white noise app on your phone or get some sound-absorbing curtains or shades to block out light and other external distractions. Also, set a regular schedule for going to bed and waking up. And create a relaxing bedtime routine, such as reading a print book or doing a calming breathing exercise before bed. Lastly, get into the habit of staying in bed for 7-8 hours every night. It’s the best way to ensure that you will reap all the benefits of a good night’s slumber.