Clouds look soft in the sky. But clouds are not made of cotton. They are made of very small water droplets, ice crystals, or both. Most of a cloud is actually air.
Water vapor is an invisible gas in the air. When moist air rises, it often becomes cooler. Some water vapor then changes into liquid water or ice around tiny pieces of dust or sea salt. Many droplets or crystals together make a cloud we can see.
Some low clouds form wide gray layers. Some high clouds look thin and white. Watching clouds gives us clues about the weather.