Molecular biology is a field of biology that looks at the molecular machinery of life. The field was founded in the early 1930s, though the phrase was only used in 1938 and the field didn't take off until the late 50s and early 60s. Since then, progress in the field has been massive.
The Ionosphere and the Exosphere (minor layers) are parts of the Thermosphere (major layer). The ionosphere is part of the theremosphere.
These are its main layers, starting with the outermost: 1  crust - relatively thin and rocky. 2  mantle - has the properties of a solid, but can flow very slowly. 3  outer core - made from liquid nickel and iron. 4  inner core - made from solid nickel and iron.