Anton van Leeuwenhoek (1632 - 1723) was a Dutch tradesman and scientist, best known for his work on the development and improvement of the microscope and also for his subsequent contribution towards the study of microbiology.
By placing the middle of a small rod of soda lime glass in a hot flame, van Leeuwenhoek could pull the hot section apart like taffy to create two long whiskers of glass. By then reinserting the end of one whisker into the flame, he could create a very small, high-quality glass sphere. These glass spheres then became the lenses of his microscopes, with the smallest spheres providing the highest magnifications.
Basic in design, van Leeuwenhoek's instruments consisted of simple powerful magnifying glasses, rather than the compound microscopes (microscopes using more than one lens) of the type used today or in Zacharias Jansen's original microscope design. Compared to a modern microscope, van Leeuwenhoek's design is extremely simple, using a single lens mounted in a tiny hole in a brass plate that makes up the body of the instrument. The specimen was then mounted on a sharp point that sticks up in front of the lens. Its position and focus could be adjusted by turning the two screws. The entire instrument was only 3-4 inches long, and had to be held up close to the eye, requiring good lighting and great patience to use.
Compound microscopes had been invented in the 1590s, nearly forty years before Leeuwenhoek was born, however there were technical difficulties in building them, meaning that early compound microscopes had a magnification of 20x or 30x. Yet although these early microscopes were much more similar in design to the modern microscopes of today, van Leeuwenhoek's simple magnifiers were able to achieve magnification of over 200x with to his skill in lens grinding, together with his naturally acute eyesight and great care in adjusting the lighting where he worked.