In general, the common notion of sleeping is simply a daily activity that allows individuals to rest for about four to eight hours everyday. Medically speaking, sleep is defined as the basic anabolic process that is characterized with absolute minimum amount of consciousness. This is also the time when a person is unresponsive to his surroundings.

Medical experts have categorized sleep into five stages. These stages are further identified into two divisions ? the REM (rapid eye movement stage) and the non-REM stage. Technically, waking is also part of the "sleep" cycle.

The "waking" stage is the part where a person is about to sleep. As one lies in bed, he or she has tense muscles due to all the daily activities and stress of the day. When an individual gets sleepier, his or her body system, including muscles, would eventually slow down. The eyes would begin to move erratically.

For some people, the "waking stage" is unnecessary and would jump to Stage 1 right away. Stage 1 is also known as "drowsiness" and lasts for about ten minutes. At this stage, the bodily activities are decreased by 50%. Most individuals would have their eyes close and can easily be awakened by outside noises or petty disturbances.

At Stage 2, a person's body temperature would decrease and his heart rate slows down. Soon after, his body would relax comfortably. Stage 3 and 4 would follow. These stages are actually where an individual is in the state of deep sleep.

When a person entered the REM stage, dreaming can actually take place. This is when there are noticeable activities in the brain that causes eye movement. Body muscles tend to relax and there are no major muscle activities. Because of the hyperactivity of the brain and the relaxed and comfortable stance of the body, dreaming usually ensue. Brain activities are heightened during the REM stage. Involuntary motions like facial movements, and muscles activities characterize this sleep cycle. It also often termed as paradoxical sleep.

One's sleeping cycle may vary from one person to another. Sleeping disorders can actually be pinpointed by mere observations of one's sleeping cycle. Physicians use polysomnograms to observe an individual's sleeping cycle in order to properly prescribed treatment and medication.