When people sleep, brain cells also enter a state of relaxation and rest, but some brain cells are not completely rested, and weak stimulation will cause their activities, thus producing dreams. For example, there is something that makes you particularly excited during the day, and you are still thinking about it before going to bed. When other nerve cells in the brain are at rest and these nerve cells are still excited, you will have a dream with similar content, which is called "thinking day and night".
If you always have strange dreams, this dream has nothing to do with your own life, and even what you dream is puzzling. This is related to liver function. When a person falls asleep, it should be "blood stored in the liver, and blood captures the soul", and the soul has a good rest in it. But these people can't stop bleeding and have some strange dreams.
However, I always have nightmares, such as dreaming that I fell from a tall building, or that I was chased, or that I dreamed of some bloody scenes, or that I was bitten by dogs and snakes. I always dreamed of some dead people, or that I fell into a dirty place. This situation is caused by the kidney, which is the main cause of human panic. If people's kidney qi or kidney essence is damaged, they often have some scary dreams. Generally, people who have these dreams have had some frightening experiences, or some changes have taken place between family and relatives.