Sleep Cycles, Explained

Sleep basically consists of two types: rapid eye movement (REM) and non-rapid eye movement (non-REM).

During a typical nights sleep, you cycle through multiple stages of REM and non-REM.

Stage 1 to stage 3 forms the non-REM sleep period, followed by REM sleep. 

Also, during sleep there are many structures of the brain that continue to work.

…dreams are also very prominent during this REM phase.