Knowledge of the microscopic structure of biological systems is the key to understanding their physiological properties. Most of what we now know about this subject has been generated by techniques that produce images of the materials of interest, one way or another, and there is every reason to believe that the impact of these techniques on the biological sciences will be every bit as important in the future as they are today. Thus the 21st century biologist needs to understand how microscopic imaging techniques work, as it is likely that sooner or later he or she will have to use one or...