I would say that they are placed into families.
The atmosphere layer closest to the earth is referred to as the troposphere. Beyond the troposphere are the stratosphere, the ozone layer, the mesosphere, and the thermosphere. The atmosphere is made up of 78% nitrogen, 21% oxygen, and smaller amounts of argon, carbon dioxide, helium, and neon.
Perestroika called for the restructuring of many aspects of the Soviet Union, for example for the restructuring of the economy. It called, among others, for more openness in communication between the government and the people.
