“On this date in 1683, Dutch scientist Antonie van Leeuwenhoek wrote a letter to the Royal Society, sharing his discovery of "animalcules," or what we know as bacteria. He was untrained in science, and had had no higher education at all, but he was acutely curious about the world around him. Starting in about 1668, he had been experimenting with lens grinding and making his own simple microscopes. He hired an artist to draw the things he saw through his lens, and he started writing informal letters to the Royal Society in 1673, describing things he'd discovered. Ten years later, on this date, he wrote a letter describing his study of the plaque found between his teeth, and the teeth of other subjects. "I ... saw, with great wonder, that in the said matter there were many very little living animalcules, very prettily a-moving. The biggest sort ... had a very strong and swift motion, and shot through the water (or spittle) like a pike does through the water. The second sort ... oft-times spun round like a top ... and ... were far more in number." Leeuwenhoek was one of the first to observe animalcules. The Royal Society was skeptical of his discovery at first, and there was much discussion about his mental status, but today he is considered "the Father of Microbiology." Leeuwenhoek never wrote any books, but he wrote letters to the Royal Society for more than 50 years. During that time, he shared his discoveries: blood cells, sperm cells, nematodes, muscle fibers, and algae. He wrote his letters in Dutch, which was the only language he knew, and his letters were translated into English and Latin before publication. He wrote right up until his death at age 90, and his last letters were detailed observations of his own final illness.”