[[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.
睡眠是一种会为身体整体带来生理上的变化的复杂现象。然而，它主要影响的是大脑。根据大脑中的电活动，睡眠被分为快速动眼期（REM）和非快速动眼期（NREM）。 NREM睡眠根据脑电波的频率和振幅再被进一步分为三个阶段。
