REM (rapid eye movement) sleep is a type of sleep that is important to humans.
This type of sleep generally occurs four or five time during one night of sleep.
The duration of each of these occurrences ranges from five minutes to forty minutes.
The periods of REM sleep become longer and longer as the night progresses.
Physical changes occur in the body to show that a person has transitioned from NREM(non-rapid eye movement) sleep to REM sleep. Breathing becomes faster,the heart rate increases,and,as the name implies,the eyes begin to move quickly.
Accompanying these physical changes in the body is a very important characteristic of REM sleep.
It is during REM sleep that dreams occur.