The sky can be full of water. But most of the time you can't see the water. The drops of water are too small to see. They have turned into a gas called water vapor. As the water vapor goes higher in the sky, the air gets cooler. The cooler air causes the water droplets to start to stick to things like bits of dust, ice, or sea salt.
Clouds get their names in two ways. One way is by where they are found in the sky. Some clouds are high up in the sky. Low clouds form closer to Earth's surface. In fact, low clouds can even touch the ground. These clouds are called fog. Middle clouds are found between low and high clouds.
Another way clouds are named is by their shape. Cirrus clouds are high clouds. They look like feathers. Cumulus clouds are middle clouds. These clouds look like giant cotton balls in the sky. Stratus clouds are low clouds. They cover the sky like bed sheets.
Most of the water in clouds is in very small droplets. The droplets are so light they float in the air. Sometimes those droplets join with other droplets.

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