Antonie van Leeuwenhoek (1632–1723) was a Dutch draper and scientist. He is best known for his improvements to the newly-invented microscope and for his pioneering work in microbiology. Using his hand-made microscopes, van Leeuwenhoek was the first to observe and describe single-celled organisms—which he called "animalcules"—which are now known as micro-organisms. He was also the first to observe blood flow in capillaries (tiny blood vessels).

High-magnification lenses

While working in his draper's shop, from 1654 onwards, van Leeuwenhoek became interested in glassmaking. Heating glass rods over a hot flame, he created long threads of glass, from which he managed to fashion tiny glass spheres. These spheres became lenses for his simple microscopes; the smallest spheres provided the highest magnifications, capable of magnifying between 275 and 500 times.