One of the more challenging things for me in high school and in college was looking for specimens under a microscope. My main difficulty back then was finding a strong enough light to illuminate the specimens; in some microscopes, the mirrors couldn't focus light onto the slides (because they're dirty or the hinges were loose) or the light source itself wasn't really good (weak sunlight thanks to cloudy days and shade from trees or the indoor lighting of the laboratory itself). Viewing specimens became even more problematic when samples were very small, like bacteria, because more light was needed to be able to look at specimens at high magnifications (at the x1000 level for the microscopes I used back then).
Then, I wonder: what was it like for Anton van Leeuwenhoek and Robert Hooke in the 1600s when they used the earliest and crudest versions of the microscope to look at plant, fungal, and microbial cells? Or for whoever used the microscope now enclosed in a glass case (below)?
I'm sure the microscopes back then were not as powerful as the compound microscopes I used back in college. And yet, these men, and others, pioneered the study of a world too small for the naked eye to see.