Everyone dreams. Sometimes you remember them crystal clearly—like you've just seen a movie—and sometimes they're so vague that they fade away even before you've opened your eyes properly. But what are dreams really, how do they come about and, above all, why do we dream?

What is a dream?

A dream is like a private movie theater in your head. Your brain creates images, sounds, and emotions without the need for the outside world. As a result, wonderful things can happen: you're cycling through the air, talking to someone who hasn't been alive for a long time, or you're suddenly in a place you've never been before. In dreams, the normal rules of time and logic don't always apply — which is what makes them so fascinating.

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