Which Dutch scientist first saw bacteria through a microscope?

Antonie van Leeuwenhoek, a draper with no university education and no Latin, who ground his own lenses to a quality nobody else matched for over a century. His microscopes were single tiny beads of glass in a brass plate, closer to a very strong magnifying glass than to a compound microscope, and they reached magnifications of several hundred times.

He looked at everything - pond water, pepper infusions, plaque from his own teeth and from two old men who had never cleaned theirs - and reported animalcules swimming about in all of it. The Royal Society did not believe him until it sent people to check, and he became a fellow without ever attending, since he spoke only Dutch.

He never told anyone how he made the lenses, and the technique died with him. Modern examination of his surviving instruments suggests he used a method of melting glass threads into spheres, and possibly a second technique he kept back deliberately. He made over five hundred and left almost no explanation - a man who could see further than anyone alive and chose not to say how, which set the field back by decades.