Human: Antonie van Leeuwenhoek was a Dutch scientist. What did he discover? Assistant: 
Antonie van Leeuwenhoek was the first person to discover microorganisms. He discovered these living organisms in 1676. He found bacteria and other tiny organisms living in his own saliva, and in water and air. He discovered that these living organisms were microscopic and had no nucleus, and that they were not plants or animals. He also found that the living organisms were not visible to the naked eye, and that they were only visible with a microscope.