Layers of the Atmosphere

Air pressure drops in half roughly every 18,000'

Troposphere ends at 40,000', along with most weather
Temperatures drop as you go up

Stratosphere is from 40,000' to 160,000'
Temperatures increase as you go up to the Ozone Layer
(heat is released when cosmic rays collide with O₂ to produce O₃)

Mesosphere is 160,000' to 260,000'
Temperatures again drop as you go up

Trivia: at 100K, air is 1% of sea level pressure, similar to the surface of Mars