Microscopy

The first microscopes were used in the 17th century to expose the microscopic world of cells and single-celled organisms for the first time. Scientific pioneers such as Robert Hooke and Anton von Leeuwenhoek, often called the “fathers of microscopy,” used homemade microscopes to study cell types from a variety of living organisms. In the late 19th and early 20th centuries, Santiago Ramón y Cajal used a microscope in combination with histology to produce highly detailed, seminal studies of nervous system structure. The microscope remains an indispensable tool in neuroscience. Because organelles, glial cells, neurons, and even populations of neurons cannot be seen by the naked eye, a microscope is essential for examining the nervous system at the cellular level. Light microscopes can enlarge the image of an object up to 1000 times greater than normal, providing access to the structure of a cell and its local environment. Fluorescent microscopes provide an even greater ability to highlight individual subcellular structures. Electron microscopes can theoretically enlarge an image one million times greater than normal, providing unparalleled insight into the smallest structures including synapses, surface receptors, and even individual proteins. The goal of this chapter is to provide a basic description of common forms of microscopy. First, we define the fundamental parameters and parts of a light microscope. Then, we survey the different forms of microscopy and why an investigator might choose one form over another. Finally, we examine issues related to processing and interpreting microscopy data. The information in this chapter will complement information in many other chapters, especially methods in Chapters 6 and 7 used to investigate neural structure and function.