Nearest part of atmosphere to earth is called:

The troposphere is the lowest layer of Earth's atmosphere. It starts at ground level and goes up to about 10 to 12 km (around 7.5 miles) on average. This layer is the densest, holding about 75% to 80% of the atmosphere's total mass and 99% of its water vapor. Humans live in this layer, and almost all weather events, like clouds and rain, happen here.