Microbiologists are concerned with forms of life that are very small, those that are microscopic or sub-microscopic in size. They study bacteria, archaea, yeasts, molds, viruses, and protozoa, looking at how they may be identified, how they cause disease, and how they are beneficial to the ecosystem.

Microbiology is a field whose challenges range from understanding virulence mechanisms of infectious bacteria and the threat of increasing antibiotic resistance to elucidating bacterial toxin structures to facilitate development of new treatments; from utilizing microorganisms to clean up environmentally devastating oil spills and toxic waste to developing microorganisms as alternative biofuels; from applying biotechnology to produce human insulin and other therapeutic proteins in yeast to constructing the next generation of vaccine-producing cells; from exploiting virus replication mechanisms to advance cancer biology research to developing computational tools to support the genomics 'revolution'.