Water is one of the key ingredients to life on Earth. About 75% of our planet is covered by water or ice.

 The water cycle is the endless process that connects all of that water. It joins the Earth's oceans, land, and atmosphere.

The oceans hold about 97 percent of the water on Earth. 

About 1.7 percent of Earth's water is stored in polar ice and glaciers. Rivers, lakes, and soil hold approximately 1.7 percent. A tiny fraction  - just 0.001 percent - exist in the Earth's atmosphere as water vapor.

The Earth's water cycle began about 3.8 billion years ago when rain fell on a cooling Earth, forming the oceans. The rain came from water vapor that escaped the magma in the Earth's molten core into the atmosphere. Energy from the sun helped power the water cycle and Earth's gravity kept water in the atmosphere from leaving the planet.