Why Do People Have Dreams When They Sleep?

The part of a person's brain called the cerebrum contains a lot of cranial nerve cells which have different responsibilities. Some are for thinking, some are for seeing, some are for listening and some are for doing things. In the daytime, when people are busy at work, the cells also do their respective work. At night when people go to sleep, the cerebrum is also in a state of rest, but the cells aren't resting. People have dreams because some of these cells are still at work. Things people thought, saw or heard in the daytime may reappear in their dreams. For example, at night when you are sleeping, if a mosquito buzzes beside your head you may dream about an airplane, or when your feet feel cold you dream you are wading across a stream.