Ernst Ruska and Max Knoll invented the electron microscope, which uses a beam of electrons instead of light to 'see' objects. Because electrons have much shorter wavelengths than photons, this microscope can magnify objects up to 2 million times, compared to the 2,000x limit of optical microscopes. This allowed scientists to see viruses, individual atoms, and the intricate internal structures of cells for the first time. It transformed metallurgy, biology, and nanotechnology. Ruska was eventually awarded the Nobel Prize in Physics in 1986 for this work, which remains fundamental to modern virology and the development of new semiconductors.