Microorganisms were first observed by Robert Hooke and Antoni van Leeuwenhoek between 1665 and 1678. In 1665, Hooke published Micrographia, which depicted the details of 60 objects as seen in the microscope. One chapter was devoted to the microfungus Mucor, the first microbe observed by the human eye. Leeuwenhoek, despite having no scientific training, became the first to observe protozoa, red blood cells, the sperm cells of animals, and bacteria, which he described in numerous letters to the Royal Society of London. In 1677, Hooke became Secretary of the Royal Society and, in the same year, confirmed some of Leeuwenhoek's discoveries. The discovery in 2006 of more than 650 pages of Hooke's missing records (the "Hooke Folio") allows us to verify the proceedings of Royal Society meetings and promises to be an important new source of Hooke's views on the renaissance of science in the 17th century.