Ask Duke Zhou, the old people seem to see yellow mud and pebbles in their eyes at night, and they look at them when they are not asleep.

This is just a dream. Dreaming is a normal and indispensable physiological and psychological phenomenon of human body. After people fall asleep, a small number of brain cells are still active, which is the basis of dreaming. Because people take the right hemisphere as the leading activity in dreams and the left hemisphere as the leading activity after awakening, waking and dreaming appear alternately during the 24-hour day and night activities of the body, which can achieve the dynamic balance of nerve regulation, spirit and activity. Therefore, dreams are a way to balance people's psychological world, especially for people's attention, emotions and cognitive activities.