Seeing the virus up close helps us understand it.
The images of SARS-CoV-2, the novel coronavirus that first appeared in humans in late 2019, were made using electron microscopy. The virus measures around 100 nanometers, and the smallest wavelengths of light that humans can see measure around 400 nanometers, meaning the virus is too small to see with a standard light microscope.
To see something that small, you need a device that uses smaller wavelengths than light. Electrons, when accelerated in a field, behave as a wave with a tiny wavelength to accomplish this.
Two electron microscopy techniques, SEM and TEM, offer different views. A Scanning Electron Microscope (SEM) scans the surface of a sample and records information that bounces back, similar to a satellite image.
A Transmission Electron Microscope (TEM) transmits electrons through a sample and projects a cross section of its inner structure. Together, these images help scientists observe the virus and how it moves in and out of host cells.