In the 1930s, when he was the head of the University of Toronto’s physics department, Eli Burton developed the first practical electron microscope. Electron microscopes use beams of electrons (rather than light) to create images. Thanks to their short wavelengths, electrons create pictures with a resolution thousands of times higher than what can be achieved with traditional light-based microscopes. These microscopes allowed scientists to observe and study materials on a molecular level for the first time.
The development of electron microscopes opened up whole new fields of research, including analyzing mining ore and studying microbiology.