What is the lowest layer of the Earth's atmosphere named?

The story behind the answer

The lowest layer is the troposphere—the part of the atmosphere we live in, extending from Earth’s surface up to about 8 km at the poles and 18 km at the equator. It’s called “tropos” (Greek for turning/mixing) because warm air rises and cool air sinks, creating constant turbulence. Nearly all weather—clouds, rain, storms—occurs here, and temperature generally decreases with height until the tropopause.

To remember the order upward: Troposphere (we “tread” on it), Stratosphere (stable “strata” with the ozone layer), Mesosphere (middle), Thermosphere (very hot, auroras). If you feel wind or see a cloud, you’re observing the troposphere at work.