The water cycle describes how water is constantly recycled through the atmosphere, oceans, and land. Energy from the sun drives this process by heating water which evaporates from bodies of water and soil into the atmosphere. Plants also release water vapor through transpiration. As the water vapor rises, it cools and condenses to form clouds. When clouds become too heavy, the water falls back to Earth as precipitation in the form of rain or snow. The precipitation is absorbed into the ground, collects in streams and rivers, and eventually returns to the oceans to continue the cycle again. The water cycle is essential for sustaining life on Earth.