Rapid eye movement sleep (REM sleep) is a normal stage of sleep characterized by the rapid movement of the eyes. REM sleep is classified into two categories: tonic and phasic. Criteria for REM sleep includes not only rapid eye movement, but also low muscle tone and a rapid, low-voltage EEG; these features are easily discernible in a polysomnogram, the sleep study typically done for patients with suspected sleep disorders. REM sleep in adult humans typically occupies 20–25% of total sleep, about 90–120 minutes of a night's sleep. During a normal night of sleep, humans usually experience about four or five periods of REM sleep; they are quite short at the beginning of the night and longer toward the end. Many animals and some people tend to wake, or experience a period of very light sleep, for a short time immediately after a bout of REM. The relative amount of REM sleep varies considerably with age. A newborn baby spends more than 80% of total sleep time in REM.[2] During REM, the activity of the brain's neurons is quite similar to that during waking hours; for this reason, the REM-sleep stage may be called paradoxical sleep.[3] This means there are no dominating brain waves during REM sleep REM sleep is physiologically different from the other phases of sleep, which are collectively referred to as non-REM sleep (NREM sleep). Vividly recalled dreams mostly occur during REM sleep. ç°ç°ç° This image I offer to you has a value:being the translation of a real R.E.M. state of mine can induct lucid "dream" only seeing - the same situations is referred happening with the paintings of a famous visionary flemish painter : Hyeronimus Bosch . Seeing theese paintings you can be inducted in state of lucid dreams. So it seems to happen with some other famous surrealists like Dali', Magritte and Max Ernst...How this happens? Not in a day...and not with the same modes for all. I have started forcing myself to find "the place": a sort of "dome" with a fire in the centre, with many luminous discs or bubbles floating inside....Catching a disk means to pass from a dreamstate to another...This operation needs balancement something difficult to explain: imagine a surfer managing his surf on a big wave (seems impossible but he can resist passing from one wave to another)..The same happens jumping from one dream to another.If you succeed in this, is much probably you got some "flash-backs" also in the awaken life much more vivids than those we commonly have of our dreams....The door is now opened to another phase...