Microbiology as a science was born in 1674 when Antony van Leeuwenhoek (1632–1723), an inquisitive Dutch drapery merchant, peered at a drop of lake water through a glass lens that he had carefully ground. It was known for several centuries previous that curved glass would magnify objects, but it took the skillful hands of a craftsman coupled with the questioning mind of an amateur scientist to revolutionize the understanding of the world in which we live. What he observed through this simple magnifying glass was undoubtedly one of the most startling and amazing sights that humans have ever beheld—the first glimpse of the world of microbes. As van Leeuwenhoek wrote in a letter to the Royal Society of London, he saw

"...Very many little animalcules, whereof some were roundish, while others a bit bigger consisted of an oval. On these last, I saw two little legs near the head, and two little fins at the hind most end of the body. Others were somewhat longer than an oval, and these were very slow a-moving, and few in number. These animalcules had diverse colours, some being whitish and transparent; others with green and very glittering little scales, others again were green in the middle, and before and behind white; others yet were ashed grey. And the motion of most of these animalcules in the water was so swift, and so various, upwards, downwards, and round about, that ’twas wonderful to see...."

It is quite surprising that not only was van Leeuwenhoek able to see bacteria, but he even described their numerous shapes (chapter opening figure). His simple microscope increased the size of the object he was viewing only about 300 times. Microscopes commonly used in the laboratory today magnify objects over 1,000 times. Seeing small objects through the lens of a microscope depends not only on magnifying the size of the specimen being viewed, but also on illuminating it. Van Leeuwenhoek must have developed an unusually good method for lighting the specimens in order to see what he reported.