The Germ Theory of Disease basically states that microorganisms are the basis of some or all disease. This theory has an interesting, long history. It arose from the work of early microbiologists and their rejection of the "spontaneous generation" concept or the concept that living germs could magically appear from non-living substances. The title of very first microbiologist would probably go to Anton van Leeuwenhoek who contributed to the genesis of the Germ Theory of Disease by observing live microorganisms (thanks to Robert Hooke's invention of the simple microscope). Later, Louis Pasteur was able to show that microorganisms are present in air but not generated by air through a series of experiments. The Germ Theory of Disease continued gaining momentum through the work of Joseph Lister, Alexander Fleming, and others. The Germ Theory of Disease was finally unequivocally proven in 1876 by Robert Koch. He demonstrated that a specific organism caused a specific disease thereby propelling microbiology into the future! The Germ Theory of Disease then cannot be solely credited to one individual, as in most science, it it the work of many over multiple years.