[[Wikipedia: Neuroscience of sleep |Sleep]] is a complex phenomenon that causes physiological changes all over the body. However, it mainly affects the brain. According to the electrical activities in the brain, sleep is divided into [[Wikipedia:Rapid eye movement sleep |rapid-eye movement]] (REM) and non-REM (NREM) stages. NREM sleep is further divided into three stages according to the frequency and amplitude of brainwaves.
睡眠是一種會為身體整體帶來生理上的變化的複雜現象。然而，它主要影響的是大腦。根據大腦中的電活動，睡眠被分為快速動眼期（REM）和非快速動眼期（NREM）。NREM睡眠根據腦電波的頻率和振幅再被進一步分為三個階段。
