By definition, microbes are organisms too small to be resolved by the unaided human eye. Thus, before the invention of the microscope by van Leeuwenhoek in the late 1600s, the vast realm of microbes went unnoticed. Since that time, both microscopes and our understanding of microbes have advanced enormously. From light microscopes to cutting-edge imaging technologies, this chapter explains many of the tools and techniques researchers use to observe the structure and function of cells. Many of the images throughout your textbook are micrographs or cartoons based on knowledge obtained from imaging technologies such as X-ray crystallography or atomic force microscopy. An understanding of how these images were obtained will deepen your appreciation for microbes and scientific research.