The troposphere is the lowest layer of Earth's atmosphere, and contains almost all of the mass (about 75-80%) of the atmosphere. The air in the troposphere is relatively warm and dense, and contains most of the clouds, precipitation and weather-related phenomena.
The stratosphere is the second-lowest layer of Earth's atmosphere and is home to the ozone layer, which protects all life from harmful ultraviolet (UV) radiation from the Sun. The stratosphere is much colder and less dense than the troposphere and is generally very stable, with little wind or weather.
