[2]. Geometrical electron optics started in 1926 when Busch [3] demonstrated that the magnetic ?eld of a rotationally symmetric coil acts as a converging lens for electrons. The importance of this discovery was s- sequently conceived by Knoll and Ruska [4] who had the idea to build an electron microscope by combining a sequence of such lenses. Within a short period of time, the resolution of the electron microscope surpassed that of the light microscope, as depicted in Fig. 1. This success resulted primarily from theextremelysmallwavelengthoftheelectronsratherthanfromthequalityof standard electron lenses which limit the attainable resolution to about 100?. Therefore, shortening the wavelength by increasing the voltage was the most convenient method for improving the resolution. However, radiation damage by knock-on displacement of atoms limits severely the application of hi- voltage electron microscopes.