It seems that all you really need to survive and feel rested is the REM phase, which is only a tiny portion of your actual sleep phases at night. You only spend 1-2 hours in REM sleep during any given night, and the rest is wasted on the other seemingly useless phases.
The way to hack yourself into entering REM sleep without being exhausted is to trick your body into thinking you’re going to get a tiny amount of sleep. You can train it to enter REM for short periods of time throughout the day in 20-minute naps rather than in one lump at night.
Remarkably, adding just one nap during the day shaves an hour and forty minutes off your total sleep requirement.
Scientific experiments and anecdotal evidence suggest that an average power-nap duration of around 1 - 2 hours is most effective.Mitsuo Hayashi, Ph.D. and Tadao Hori, Ph.D.have demonstrated that a nap improves mental performance even after a full night sleep.
REM sleep, this particular sleep state is highly conducive to fluid reasoning and flexible thought.
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 4 or 5 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.
During REM, the activity of the brain's neurons is quite similar to that during waking hours. Vividly recalled dreams mostly occur during REM sleep.
....the link between creativity, dreams, and sleep behaviors, researchers discovered that participants who were classified as "fast sleepers" (those who fell asleep quickly) were more likely to score highly on a creativity test, participants who scored highly on a creativity test were more likely to solve their problems through dreams and to fall asleep quickly, and adults in creative occupations have significantly more dream distortion, visual mentation, and regressive dream content
........after sleep there is an increased insight, that is, a sudden gain of explicit knowledge. Thus during sleep the representation of new memories are restructured.