The resolution of any imaging microscope is ultimately limited by di?raction and can never be signi?cantly smaller than the wavelength ? of the ima- forming wave, as realized by Abbe 1] in 1870. In a visionary statement, he argued that there might be some yet unknown radiation with a shorter wa- length than that of light enabling a higher resolution at some time in the future. The discovery of the electron provided such a radiation because its wavelength at accelerating voltages above 1 kV is smaller than the radius of the hydrogen atom. The wave property of the electron was postulated in...