Anton van Leeuwenhoek is often credited as being the inventor of the microscope, but that is not actually the case. It would also be unfair to remember him for that and that alone, because his contributions to microbiology were far more extensive and important.
He was born on October 24th 1632 in Delft, Holland, and had an adequate, although by no means advanced, education. He started in business as a linen draper, and was clearly a success at his trade. He was a contemporary of the painter Vermeer, and may well have been a friend of his. His interests clearly extended well beyond the linen trade, because he learned how to grind glass magnifying lenses, and was exceptionally good at so doing, helped by his acute eyesight. Many of his lenses were extremely small, and were made from glass strings that then formed spherical globules as they cooled.
He made more than 500 simple microscopes in his lifetime, although these used single lenses, as opposed to the double-lens compound microscopes that were already in use at the time. However, what distinguished his instruments was the quality of the lenses, which gave up to 200 times magnification, which was considerably better than that of the compound microscopes then available. It has also been suggested that some of his instruments achieved far better magnifications, possibly as much as 500 times. He also experimented with many different designs of microscope, although only a handful have survived to the present day.
Leeuwenhoek's real contributions to microbiology came not just from his microscopes but, even more, from the uses to which he put them. He made observations of anything that took his interest, had drawings made of what he saw, and sent details of his observations to the Royal Society in London. His letters, which had to be translated from Dutch into English before the London scientists could understand them, spanned 50 years, from 1673 until his death at the remarkable age, for his time, of 90.
He had little understanding of what he was seeing, having had no scientific training, but that was part of his value to science, because his descriptions were made entirely free of assumptions. For example, he observed "an unbelievably great company of living animalcules" in tooth plaque, without appreciating that these were bacteria. Of course, nobody else knew their significance in causing disease either, as he was the first person to observe and describe them.
His other discoveries included algae, blood cells, sperm cells, foraminifera, nematodes and rotifers. He observed blood flow in capillaries and the pattern of muscle fibers. Aside from microbiology, he also examined mineral crystals and fossils.
His discoveries helped to dispel many myths that were then current as explanations of natural phenomena, such as that grain weevils were spontaneously created, and that mussels and other shellfish were produced by sand.
Many of his early discoveries were doubted by the people who read his papers, and a delegation was sent to Delft by the Royal Society to see how van Leeuwenhoek was producing all this material. However, once he was able to demonstrate his methods at first hand, his subsequent work was eagerly awaited, and he was elected as a Fellow of the Royal Society in 1680, although he never attended a meeting. His lasting contribution to microbiology was therefore the conviction that observation, rather than guesswork and theory, must lie at the heart of science in this field.