It was Antonie van Leeuwenhoek's invention of the microscope, and his subsequent discovery of what he dubbed "animalcules," that changed human perception of infectious disease forever. When I was a kid, one of my books was "Pioneer Germ Fighters," I'd recommend it to anyone who is interested in teaching the history of Immunology to their kids. Or learning it themselves for that matter. It's never too late to learn stuff.