Atmosphere

From Wiki 5A

An atmosphere is a layer of gases that surround a planet. On Earth, this is where all weather occurs. The atmosphere's highest layer (out of four layers) is the Exosphere, and the lowest layer is the Troposphere. The next layer is the Stratosphere. The third layer is Mesosphere. The fourth layer is the Thermosphere. The Troposphere is the only layer that you can breathe in.