Antony van Leeuwenhoek is best known for discovering bacteria and creating more than 500 simple microscopes. He also discovered sperm cells, blood cells, protists and microscopic nematodes.
Antony van Leeuwenhoek made one of the first recorded observations of bacteria when he studied the plaque from his teeth and the teeth of several other people. He noticed "animalcules" swimming in the saliva sample.
His simple microscopes were very different from the compound microscopes used today. They had one lens and a brass plate, and the lens was adjusted by turning two screws. Only about 10 of these simple microscopes are still in existence today.
Although van Leeuwenhoek never received a degree or any formal scientific training, he was elected a member of the Royal Society of London in 1680.