Clouds are large accumulations of small water droplets or ice crystals that form in the sky. Clouds form through the process of evaporation and condensation as warm air rises and cools. They appear white when they reflect sunlight but turn gray when the cloud is thick and all light cannot pass through. Clouds move across the sky with wind. A small cloud can be created in a jar by adding water, food coloring, and creating temperature changes that allow water vapor to condense into droplets, simulating the natural cloud formation process.