Final answer:
Antonie van Leeuwenhoek was the first person to develop powerful microscopes and observe bacteria, yeast plants, and living organisms.
Step-by-step explanation:
The first person to develop powerful microscopes that allowed them to see and study bacteria, yeast plants, and living organisms through a single droplet of water along with the circulation of blood corpuscles in capillaries was Antonie van Leeuwenhoek. He was a Dutch cloth merchant who developed a lens powerful enough to view microbes in the 17th century. Van Leeuwenhoek's microscope was more sophisticated than the compound microscopes of his time and he observed and described single-celled organisms, bacteria, and protists, which he called 'animalcules'.