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.
There are 3 MAIN layers. 1) The crust (top layer) 2) Mantle(biggest layer) 3) Core (the hardest part of earth were the magma is stored.) There is 5 layers if you want Technicalchnical. 1) the crust - thin, rock material. 2) the outer mantle - dense and mostly solid rock. 3) the inner mantle - dense and solid rock.