Humans have long known that glass bends light. However, it took us awhile to figure out that stacking lenses in a tube would open up a whole new world to science, finally allowing us a peek at the microscopic.

After completing a fairly extensive survey of bacterial and viral pathogens, it's time to learn about some other more general microbiology concepts. What better place to start than the indispensable tool of the microbiologist, the...