Anton van Leeuwenhoek. Caricature of the Dutch microbiologist Anton van Leeuwenhoek (1632-1723), looking through a magnifying glass to represent his discoveries in microbiology. He devised a method for making microscopes quickly and cheaply, and used his devices to study the natural world. He was the first to see single-celled animals, which he called animalcules, and he also noted bacteria, blood cells and sperm cells.