- Van Leeuwenhoek first observed a magnifying glass used by textile merchants in Amsterdam during his apprenticeship in 1653. Van Leeuwenhoek made many improvements over the simple magnifier he first encountered. He hit upon a method for making tiny but powerful lenses and created microscopes of many designs.
- The most powerful surviving example of van Leeuwenhoek's work has a magnification of 275x. By 1673, his discoveries led to the publication of some of his observations in the Philosophical Transactions of the British Royal Society, the premier scientific journal of the time. This date is usually taken as the "official" date of the invention of the microscope.
- Among the more significant of van Leeuwenhoek's discoveries were single-celled organisms (protists), bacteria, sperm cells and the striations found in muscle fibers.
- Erroneous reports often describe van Leeuwenhoek as having learned to grind the small lenses he used in his microscopes. Instead of grinding them, he made lenses by melting glass in a flame and forming small, round beads that served as his lenses.
- Van Leeuwenhoek's reports of microscopic life were initially met with skepticism, because microscopic organisms were completely unknown prior to his discovery of them. After sending a team of observers to Delft to verify van Leeuwenhoek's discoveries, the Royal Society confirmed his observations in a publication in 1680.
