The water cycle is the continuous movement of water on, above, and below the surface of the Earth. It starts with evaporation, where heat from the sun turns water from rivers, lakes, and oceans into vapor. This vapor rises into the atmosphere, where it cools and condenses into tiny droplets, forming clouds. When the droplets become heavy enough, they fall back to the ground as precipitation, which can be rain, snow, or hail. This water then flows into rivers and lakes, or soaks into the ground, replenishing aquifers. The cycle repeats, ensuring that water is always available for plants, animals, and humans.