In 1675, Antony van Leeuwenhoek, an unlearned haberdasher from Delft, placed a drop of rainwater under his microscope and detected thousands of tiny animals in it. Leeuwenhoek proceeded to examine the microscopic activity of his spitle, teeth plaque, and faeces, and as a result of his findings the field of bacteriology was born. Some 200 years later, Wilhelm Conrad Roentgen, a professor of theoretical physics at the University of Wurzburg, invited his wife to his laboratory, asked her to place her hand on an unexposed photographic plate, turned on an electric current, and showed her a picture of the bones of her hand - and so came the X-ray. This text describes these and eight other medical discoveries throughout history, bringing to life the scientific pioneers responsible for them and the excitement, frustrations and jealousies that surrounded the final achievements.