There’s more to sleep than simply conking out for eight hours.
If you never realized this, well, we forgive you. After all, it seems rather uncomplicated: You sleep, you wake up, you repeat.
But dig deeper , let’s take a closer look at the sleep cycle. It consists of four main sleep stages, progressing from stage 1 through to REM. A night of sleep typically contains between three and five of these cycles, which each range in time from 90-110 minutes.