You're lying on the grass, watching a cloud that looks exactly like a dragon. You blink — and now it's a shoe. What's going on up there?

Clouds aren't solid things like rocks or pillows. They're made of billions of tiny water droplets — each one smaller than the period at the end of this sentence — all floating together in the sky.

Those droplets are light enough to drift on the wind. And wind up in the clouds never stops moving — it swirls and tumbles and changes direction constantly, like invisible rivers flowing in every direction at once.

So when the wind blows through your dragon cloud, it pushes some droplets left, pulls others right, lifts a clump here, stretches a wisp there. The dragon's tail gets thinner. Its head puffs out.

At the same time, new droplets are always forming at the bottom of the cloud where warm air rises up, and old droplets are always evaporating — turning back into invisible water vapor — at the cloud's edges where the air is drier.

It's like the cloud is being rebuilt in real time. Every few seconds, some droplets vanish, new ones appear, and the wind rearranges what's left. The cloud you're looking at now isn't quite the same cloud it was ten seconds ago.

Fast winds make clouds change fast — a thundercloud can twist into five different shapes in a minute. Slow gentle winds make clouds drift lazily, their edges softening like cotton candy pulled apart.

So your dragon became a shoe because a gust of wind blew through it, a few million droplets evaporated off the snout, and a new puffy section formed right where a shoe's toe would be. The sky's always painting something new.