ALIS Corporation has developed a new helium ion microscope which has many advantages over both traditional scanning electron microscopes (SEMs) and focused ion beams (FIBs). This new technology is expected to produce an ultimate focused spot size of 0.25 nm. This high resolution is attributed to the high source brightness (B > 4 x 10(9) A/cm(2) sr), low energy spread (Delta E/E similar to 2 x 10(-5)), and small diffraction effects (lambda similar to 80 fm). The interaction of helium ions with matter offers several valuable contrast mechanisms and a surface interaction volume which is much smaller than a SEM or conventional FIB. (c) 2006 American Vacuum Society.