Environmental microbiology is the scientific study of microorganisms in the environment. This discipline includes air microbiology, soil microbiology, and water microbiology. Environmental microbiology is that the study of the composition and physiology of microbial communities within the environment. The environment during this case means the soil, water, air, and sediments covering the earth and may also include the animals and plants that inhabit these areas. Environmental microbiology also includes the study of microorganisms that exist in artificial environments like bioreactors. Molecular biology has revolutionized the study of microorganisms in the environment and improved our understanding of the composition, phylogeny, and physiology of microbial communities. The current molecular toolbox encompasses a variety of DNA-based technologies and new methods for the study of RNA and proteins extracted from environmental samples. Currently, there is a major emphasis on the application of "omics" approaches to determine the identities and functions of microbes inhabiting different environments.