Antonie van Leeuwenhoek

Antonie Philips van Leeuwenhoek was raised in Delft and worked as a draper, opening his own shop in 1654. He took up lensmaking as a side interest, and in the 1670s began peering through single-lens microscopes of his own design at anything he could scrape or scoop. What he saw - microbes he called "dierkens," bacteria, spermatozoa, red blood cells, muscle fibers, blood moving through capillaries - had never been documented. He was the first to observe and experiment with these organisms, the first to gauge their size. Van Leeuwenhoek never wrote a book; instead he sent chaotic, detailed letters to the Royal Society, which published them in Philosophical Transactions. By the time he died in 1723, the self-taught shopkeeper had cracked open microbiology as a discipline.