Learn why clouds are critical to Earth's climate system and explore how they form, in this video from NOVA's Cloud Lab. Visualizations show how the Sun warms Earth's surface, driving the water cycle. The processes of evaporation and transpiration transport water from Earth's surface into the atmosphere as water vapor. As air rises and cools, the relative humidity increases. If it reaches a state called supersaturation, water vapor changes from gas to liquid, forming water droplets or ice crystals around dust and other particles, creating a cloud. When the water droplets become large enough, they fall back to Earth's surface as precipitation.

This video is available in both English and Spanish audio, along with corresponding closed captions.