An electron microscope is a special microscope that uses electrons instead of light to make very small things visible. Normal light microscopes reach their limits when it comes to tiny structures because their light waves are too large to clearly show individual atoms or molecules. Electrons, on the other hand, have a much shorter wavelength, which means that electron microscopes can deliver extremely sharp images – down to individual atoms.
In a scanning electron microscope (SEM), an electron beam is “scanned” across the surface of the sample, i.e., scanned line by line. When the electrons hit the sample, they collide with the atoms and generate various signals – for example, backscattered electrons or secondary electrons.
These signals are detected by special detectors and converted into an image that is visible on a screen. This creates a very detailed 3D-like image of the surface of the sample, revealing tiny structures that are far smaller than could be seen with light microscopes.
An electron microscope can be used, for example, to observe cells, viruses, or material structures on a nanometer scale – i.e., millionths of a millimeter. This makes it an indispensable tool in research, medicine, and materials science for examining the tiny building blocks of our world in greater detail.