Microscopy is the field of using microscopes to view objects. There are three well-known branches of microscopy, optical, electron and scanning probe microscopy.
The term resolution is the minimum distance between distinguishable objects in an image, although the term is loosely used by many users of microscopes and telescopes to describe resolving power.
Virtual microscopes can emulate a scanning electron (or other) microscope and they allow users to zoom up to 3,600X magnification and focus into a variety of built-in microscopic samples.
Optical or light microscopy involves passing visible light transmitted through or reflected from the sample through a single or multiple lenses to allow a magnified view of the sample.
Optical microscopes, through their use of visible wavelengths of light, are the simplest and hence most widely used type of microscope.
Typical magnification of a light microscope is up to 1500x with a theoretical resolution limit of around 0.2 micrometers or 200 nanometers.
An electron microscope is a type of microscope that uses electrons to illuminate a specimen and create an enlarged image. Electron microscopes have much greater resolving power than light microscopes and can obtain much higher magnifications. Some electron microscopes can magnify specimens up to 2 million times, while the best light microscopes are limited to magnifications of 2000 times.
Low temperature scanning electron microscope a snow crystal courtesy of: Wikimedia
Scanning Probe Microscopy
Scanning probe microscopy (SPM) is a branch of microscopy that forms images of surfaces using a physical probe that scans the specimen. An image of the surface is obtained by mechanically moving the probe in a raster scan of the specimen, line by line, and recording the probe-surface interaction as a function of position.
Examples of scanning probe microscopes are the atomic force microscope (AFM), the scanning tunneling microscope and the photonic force microscope.