I'm sure your teacher wants your speculation. To help you, read about the discovery of "animalcules."
http://www.leben.us/index.php/component/content/article/59-volume-3-issue-4/236-antoni-van-leeuwenhoeks-amazing-little-animalcules
(a) Speculate about how the invention of the microscope
might have helped doctors to understand what caused
diseases.
2 answers
how the invention of the microscope might have helped doctors to understand what caused diseases.