In which year was the electron microscope first used to visualize viruses?

The electron microscope was first used to visualize viruses in the 1930s. In 1935, the tobacco mosaic virus was the first virus to be observed using an electron microscope by British biophysicist and Nobel laureate, Sir John Bernal. The use of electron microscopy revolutionized the field of virology, enabling scientists to study viruses in much greater detail than was possible with a light microscope.