There are certain kinds of bacteria that you need to stain, because otherwise they are nearly perfectly transparent, but there are lots of larger bacteria that

There are certain kinds of bacteria that you need to stain, because otherwise they are nearly perfectly transparent, but there are lots of larger bacteria that you can see well with even a fairly cheap microscope, of the type that teenagers use in school. Indeed, when I was 15 years old, I remember watching a lot of single celled organisms crawl around in the microscope that I was assigned at school. Although most bacteria tend to be on the smaller side of single celled organisms, some larger bacteria are still easy to see, even with such cheap microscopes.