There are several different classes of microscopes. However, the most common way to categorize these devices is based on what interacts with the sample, be it light (or photons), electrons, or a probe. These classes are referred to as optical, electron, and scanning probe microscopes, respectively.

That said, you often see microscopes categorized according to the wavelength used to magnify an image as well. Common wavelengths include visible light, ultraviolet light, x-rays, and electrons. For example, if a microscope uses visible light to illuminate a sample, it’s typically referred to as a light microscope. If fluorescence is used, the microscope is referred to as a fluorescence microscope.

The most common types used across laboratories today are light microscopes, or optical microscopes, which utilize visible light, along with a series of lenses, to achieve magnification.

Electron microscopes, which employ beams of electrons as the light source, often serve as an alternative to light microscopes because, compared to visible light, electrons have significantly shorter wavelengths. Around 100,000 times shorter, to be more exact.

The use of shorter wavelengths increases resolving power and magnification, allowing for extremely high resolution of objects too small to be seen by standard microscopy methods like light microscopy. For this reason, electron microscopy is a powerful tool in several fields and industries where highly detailed imaging is required to understand a biological or nonbiological sample’s ultrastructure (fine structure, especially within a cell, that cannot be seen with standard light microscopes).

Areas within the life sciences that rely on electron microscopy include structural biology, drug discovery and development, materials science, microelectronics, nanotechnology, and forensics science.