A major breakthrough in the study of cells came with the development of electron microscope. This is because

Electron beam can pass through thick materials, whereas light microscopy requires thin sections

The electron microscope is more powerful than the light microscope as it uses a beam of electrons which has wavelength much longer than that of photons

The resolution power of the electron microscope is much higher than that of the light microsope

The resolving power of the electron microscope is 200-350 nm as compared to 0.1-0.2 nm for the light microscope