Which microscope did Anton van Leeuwenhoek use to observe single celled organisms?

By heating the center of a small soda glass rod over a flame, Leeuwenhoek was able to pull apart the two ends of the rod, causing it to elongate into thin whiskers. He then heated the end of the whisker to produce a tiny, high-quality glass sphere, which he used as the lens for his microscope, with the smallest sphere offering the highest magnification.

The rudimentary designs of Leeuwenhoek consisted of a single lens set in a tiny hole on a brass plate, on which the specimen was fixed, with its position and focus adjustable by turning two screws. The specimen was set up on a sharp point protruding in front of the lens.

The entire device, which measured between three and four inches in length and needed to be held up close to the eye, was extremely patient to use and needed good lighting.

Utilizing a basic microscope, Anton van Leeuwenhoek examined single-celled organisms.