Clouds

weather · water cycle · sky

Made of water. Clouds are mostly composed of microscopic droplets of liquid water or ice crystals suspended in the air. Each droplet is so small that millions could fit on the head of a pin.

Born from cooling air. Clouds form when warm air rises and cools down until it reaches its dew point, the temperature where water vapor turns into visible liquid droplets. This usually happens high in the atmosphere where it's much colder.

Needs moisture to grow. Air can only make clouds if it has enough water vapor in it, either from evaporation off oceans and lakes or from moisture in the air around it. When the dew point temperature matches the actual temperature, clouds appear.

Found everywhere. Earth's clouds are made almost entirely of water, but other planets in our solar system might have clouds made of different materials. Clouds are essential for the water cycle that brings rain and fills our rivers and lakes.

Visible in the sky. What makes a cloud visible is the sheer number of tiny droplets and crystals all clustered together, which scatter light and create the white or gray appearance we see from the ground.