Humans live in the layer of the atmosphere referred to as the troposphere. Most of the mass of the atmosphere can be found in the troposphere.
There are five layers to the Earth's atmosphere. The troposphere is the first layer above the surface and is where the weather of the Earth occurs. The troposphere is heated from below as sunlight warms the ground or ocean, which in turn then radiates the heat into the air. This warm air tends to rise, keeping the air in the troposphere turbulent. The top of the troposphere is very cold. The average temperature there is around -64 degrees Fahrenheit.