A major breakthrough in cell biology was achieved with the invention of the electron microscope because its resolving power is much higher than that of a light microscope. Resolving power is inversely proportional to the wavelength of the radiation used. Since the wavelength of an electron beam is significantly shorter than that of visible light photons, the electron microscope can resolve much finer details of cell organelles. Option B is incorrect because the values are swapped (light microscope has a resolving power of ~200 nm, while electron microscope has ~0.1 nm). Option C is incorrect because electron beams have low penetrating power and require ultra-thin sections. Option D is incorrect because the wavelength of electrons is much shorter than that of photons.