Castner, Ratner et al. have just published an important paper that discriminates amongst different cell types at the single cell level. They used C60 etching to remove the overlayer junk from the lawn of cells, and principle component analysis to look for chemical differences. The image quality was dramatically improved with the C60 treatment. The samples were freeze-dried, and the authors acknowledge this could lead to some artifacts. I am a bit concerned that they do not talk about the higher mass ions - in the lipid region from m/z 500-900. It seems to me that getting these distributions at the single cell level is the holy grail of mass spec imaging right now.