Microbiology is the study of the invisible world of microorganisms, organisms so small that microscopes and other special equipment are needed to directly observe them. They play a crucial role in maintaining the Earth's atmosphere and help decompose organic matter. Microbiology plays a role in a great variety of areas, including optimizing soil for agriculture, developing preservatives and pharmaceuticals, genetic engineering, and developing climate change models. The discovery of microbes was instrumental in controlling infectious disease outbreaks that had, for centuries, wiped out entire populations.