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.
Dr Eric F Greif et al. The left horizontal (or minor) fissure is an accessory fissure. In a prospective study of 2,000 consecutive normal chest X-rays (AP and lateral), a definite left horizontal fissure was identified in 1.6% of the subjects 1. Article: