Ion source and method of making and sharpening. The ion source is a single crystal metal conductor having a substantially conical tip portion with substantial rotational symmetry. The tip portion terminates with a tip radius of curvature in the range of 50 100 nanometers. The ion source is made by electrochemical etching so that a conical tip of a selected geometry is formed. The ion source is then sharpened to provide a source of ions from a volume near the size of a single atom. Further, this ion source makes possible a stable and practical light ion microscope which will have higher resolution than existing scanning electron microscopes and scanning metal-ion microscopes.