<human>:  Why did the Dutch scientist Antonie van Leeuwenhoek use a microscope?
<bot>: Antonie van Leeuwenhoek was a Dutch scientist. He invented the microscope. His microscopes were made of brass and were able to magnify objects up to 400 times their actual size. He was the first person to describe bacteria, and he is credited with being the first person to describe the existence of protozoa, such as amoebas and flagellates.