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Microbiology can be said to have begun with the development of the microscope. Antonie van Leeuwenhoek, a Dutch draper, was the first to provide proper descriptions of his observations, "animalcules," as he called them.

The early Greeks believed that living things could originate from nonliving matter; the goddess Gea was credited with creating life from stones. Although Aristotle discarded this notion, he still held that animals could arise spontaneously from other unlike organisms or from soil. His influence regarding this concept of spontaneous generation was still felt as late as the 17th century. Toward the end of the 17th century, a chain of observations, experiments, and arguments began that dealt a deathblow to the idea that life could be generated from nonlife.

Although Francesco Redi, an Italian naturalist, disproved that higher forms of life could originate spontaneously, proponents of the concept claimed that microbes were different and did indeed arise in this way. Such illustrious names as John Needham, Lazzaro Spallanzani, Franz Schultze, and Theodor Schwann figured in the debates.

It remained for Louis Pasteur to settle the matter. He proved in a series of masterful experiments that only pre-existing microbes could give rise to other microbes--at least under current earthly conditions (that life arose spontaneously from nonlife at some earlier time, under appropriate physical and chemical conditions, is an undisputed postulate of chemical evolution).

Regarding microbes and disease, Girolamo Fracastoro, an Italian scholar, advanced the notion as early as the mid-1500s that contagion is an infection that passes from one thing to another. The "thing" that is passed along eluded discovery until the late 1800s, when the work of many scientists, Pasteur foremost among them, determined the role of bacteria in fermentation and disease. Robert Koch, a German physician, defined the procedure for proving that a specific organism causes a specific disease.

The foundation of microbiology was securely laid during the period from about 1880 to 1900. The students of Pasteur, Koch, and others discovered in rapid succession a host of bacteria capable of causing specific diseases (pathogens) and elaborated an extensive armamentarium of techniques and laboratory procedures for revealing the ubiquity, diversity, and power of microbes.

All of these developments occurred in Europe. Not until the early 1900s did microbiology become established in America. Many of the microbiologists who worked in America at this time either had studied under Koch or at the Pasteur Institute, in Paris. All microbiologists of the early 20th century, however, were influenced by such men as Koch. Once established in America, microbiology flourished, especially with regard to such related disciplines as biochemistry and genetics. Since the 1940s, microbiology has experienced an extremely productive period, during which many disease-causing microbes have been identified and methods to control them have been developed.

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