Dreaming is an inherent phenomenon and it is impossible for a normal person not to dream. People generally divide sleep into NREM 1, 2, 3, 4 and REM stages. It has been found that dreaming mostly occurs in the REM stage, but it can also occur in other sleep stages. Studies have confirmed that REM sleep plays an important role in memory preservation and reprocessing, and it contributes to the development of brain function. Therefore, it is not correct to generalize that dreaming is harmful to health. There is some truth in the saying “when you think about something, you dream about it at night”. It is not uncommon for some people to get inspiration and good phrases in their dreams. Freud believed that dreams reflect content that generally symbolizes human desires, while more research suggests that dreams can involve various aspects that may be related to daytime considerations, emotional reactions, physical discomfort, sexual orientation, and many other aspects. It is not, as some people say, “the opposite of reality”, but often, through the subconscious, its content becomes more subtle and symbolic, reflecting its true meaning in another form or episode. For example, people often dream that they are slowly flying in the sky, the real meaning of which is actually the need for sex. Some people have frequent dreams and nightmares, which may be related to physical ailments, mental and environmental disturbances. Physical pain, breath-holding, palpitations, anxiety and frequent urination can all cause corresponding dreams. If you often dream of unpleasant content such as pain and divorce, you may have to be alert to physical or mental illnesses such as heart disease. It is thus clear that dreams are highly reactive and can integrate many of the many differences in content. In dreams, we can easily believe the dream episodes without ever doubting them, and act without shame, and mostly forget them quickly after waking up, all related to the function of aminergic neurons in our brain, which are the least active during sleep. Others have had the experience that some dreams can be remembered and some cannot. This has to do with the time of dreaming. Generally, dreams awakened during the REM period can be recalled clearly, and the closer the time of dreaming and the time of awakening, the clearer the memory, and vice versa, the more blurred. From this we can see that although the content of dreams is varied, there is a systematic connection between dreams and waking thought. Dreaming allows our mental activity to bridge the gap between wakefulness and sleep. But we should also realize that we still have a long way to go to gain a deep understanding of the physiological mechanisms of dreams.