Why do we dream?

You fall asleep, snug under your blanket. Then suddenly you are flying, or splashing in a pool, or talking to a friendly dragon! Where do these strange night-time stories come from?

Your brain stays awake

Even while you sleep, your brain keeps working. It is like a tidy helper who waits for quiet time to sort everything out. During the day you see, hear and feel so much. At night your brain looks at all of it and decides what to keep.

Dreams are mixed-up memories

To do its tidying, your brain plays back bits of your day. It picks up a memory here, a feeling there, and mixes them together. The dog you saw, the cake you ate and the song you heard can all get stirred into one funny story. That story is a dream.

That is why dreams feel so silly. They are pieces of real things, jumbled up in a new way — like shaking a box of puzzle pieces from different puzzles.

Why we forget them

When you wake up, the dream often slips away fast. Your brain was just practising and sorting, not saving the dream itself. So by breakfast, most dreams have floated off, like soap bubbles popping in the sun.

Wonder fact: You dream most during a stage of sleep called REM, when your eyes wiggle quickly behind your closed lids — even though you are fast asleep!