Scanning electron microscopy with beam energies below 2 keV offers the possibility to image uncoated nonconducting specimens. However, the resolution at such low energies is rather poor in conventional microscopes. We discuss the individual contributions to the resolution limit. Based on the results of this discussion we propose new electron-optical components to improve the resolution at low beam energies. Using these elements a resolution limit of 1 nm can be obtained at an electron energy of only 500 eV.