In general, deep sleep accounts for about 20% of total sleep time, usually 2-4 hours is appropriate. Sleep is divided into non-rapid eye movement (NREM) and rapid eye movement (REM) sleep. Normal sleep is firstly non-REM sleep, according to the depth of sleep and the degree of EEG slow wave, NREM can be divided into four stages, which are pre-sleep, light sleep, moderate sleep, deep sleep, and generally categorized as deep sleep in stages 3 and 4. NREM and REM alternate for one cycle each time, 4-6 cycles per night, REM sleep accounts for 20%-25%, NREM sleep in stages 3 and 4 accounts for about 20%, mainly in the first half of sleep, and NREM sleep stages 1 and 2 are mainly in the second half of sleep, thus making it easy to wake up in the morning. Sleep is an important part of the body’s recovery, integration and consolidation of memory, which is very important for human health. Before going to bed, you can listen to some soothing music, or foot baths, yoga, etc., to help sleep.