Answer:
Observe mircroorganisms, specifically bacteria.
Explanation:
Antonie Van Leewenhoek is known to be the "Father of Microbiology." He observed them using his own version of the microscope. He called them animalcules. He used his microscope to count the number of microorganisms he observed in samples of water. It was on September 17, 1676 when he proclaimed that bacteria existed.
