<human>:  Antonie van Leeuwenhoek was a Dutch scientist. What did he discover?
<bot>: Antonie van Leeuwenhoek was the first person to discover microorganisms. He was born in 1632 in Delft, Netherlands. He worked as a merchant, and he made a microscope from a lens he found in the workshop of a local goldsmith. He observed and described various bacteria, protozoa, and fungi. He also discovered spermatozoa and bacteria in semen.