R.E.M. (rapid eye movement) study, is used by sleep researchers to analyze the type of wave functioning inside a human's mind during sleep. There are several waves, and each represents a different level of sleep. The pre-stage of the sleep would be the alpha waves. The brain wave activities indicate that the human mind is awake and relaxed. as the mind gradually adapts to this, breathing rate slows and the brain waves slow further, as irregular waves are appearing; this is considered stage one. Soon after the mind is more relaxed ( approximately twenty minutes of sleep) stage two is reached. Stage two is characterized by a periodic appearance of sleep spindles or bursts of brain wave activity. At this stage, the mind can be awakened but it is clear that you are in deep sleep.

In the next few minutes, the mind is going  through the transition of stage three to deep sleep in stage four. During stage three and increasing in stage four, our brain "emits" large waves called delta waves. The delta waves last for approximately thirty minutes.

For approximately an hour we fall asleep, then a strange thing happens. We assume that we should continue on and on into deeper sleep, but actual we go back to the sleep ladder. It goes back through stage three and two, and then enters the "most intriguing sleep phase of all; "the R.E.M. stage sleep. In about ten minutes of R.E.M. stage, our brain waves become more rapid; increase sleep, similar to stage one. The difference of stage one and R.E.M. stage is that our heart rate rises, our breathing becomes more rapid and irregular, and every half minute or so, our eyes move around in a momentary burst of activity behind our closed eyelids. This is when dreaming has been reported to occur. It is quite obvious that sleep observers can notice these R.E.M. bursts, but it was amazing that R.E.M. wasn't discovered until 1952.