The water cycle is a continuous process that involves the exchange of water between the earth's surface and the atmosphere. It begins with the sun's heat causing water to evaporate from oceans, lakes, and rivers. This water vapor rises into the atmosphere where it cools and condenses into clouds. The process of water vapor turning into clouds is called condensation. As the clouds become denser, the water droplets combine, and when they become heavy enough, they fall back to the earth's surface as precipitation, which can be in the form of rain, snow, or hail. When the precipitation falls on the ground, it can either soak into the soil or run off into rivers and streams, eventually making its way back to the oceans. The water that does not evaporate or run off remains on the earth's surface as liquid water until it evaporates once again, starting the water cycle over.