Why does the brain dream, science can not explain, the brain dreaming since ancient times, many healthy people in sleep will appear to dream this situation. Generally, if dreaming is not particularly frequent and there are no nightmares to wake up, it is a normal phenomenon. The brain alternates between fast and slow waves during sleep, and when fast waves occur in the brain, it is called the rapid eye movement period, during which dreaming often occurs, which is a normal reaction. In addition, if patients are deeply stimulated by life events or diseases, they can aggravate the phenomenon of dreaming, such as daytime work or thinking deeply about something, which will lead to dreams at night, and some patients who are deficient in qi and blood will often appear to dream, or even nightmares of this phenomenon.