depends on the magnification you are looking for... usually, a light microscope is enough (1000x max magnification)...
An electron microscope is powered by high energy beams and can magnify many times higher than the light microscope (where magnification is limited by the wavelength of light). The magnification of an EM is on the nano scale.
(P.S.: as a chemist, I'd always choose an EM over an optical microscope as I can always zoom in or out depending on my needs) ;)
