Dreams have fascinated since the dawn of mankind. Some people are able to discover in them predictions of the future, others see them as a bundle of tangled threads that are a remnant of a difficult day and the problems of everyday life. Some eminent people have found in them the inspiration for their works and brilliant ideas. Studied by psychoanalysts and neurologists, they still remain one of the unsolved scientific puzzles. The following article describes several possible hypotheses as to where moving images come from in our heads while the body is resting.