On Earth, clouds are formed as a result of saturation
of the air when it is cooled to its dew point, or when it gains
sufficient moisture, usually in the form of water vapor, from an
adjacent source to raise the dew point to the ambient temperature.
Clouds are seen in the Earth's homosphere, which includes the
troposphere, stratosphere, and mesosphere. Nephology is the
science of clouds, which is undertaken in the cloud physics branch of
meteorology. The World Meteorological Organization uses two methods of
naming clouds in their respective layers of the homosphere, Latin and
common name.