REM Sleep

In adults, REM sleep is a short phase that makes up only about 20 percent of the total amount of time spent in slumber. 

During REM sleep, the brain is not only in a state of heightened activity, it is also no longer governed by the regions that control logic and inhibit impulses. Unconstrained by reality, fragments are loosened from their original context and recombined in strange, exhilarating, and sometimes frightening ways. It is all very vivid and emotionally intense, as the unbelievable becomes believable.