Additionally, we omitted metal stains typically added to plastic sections that react with specific functional groups in biomolecules. For example, osmium tetroxide stains membranes, uranyl acetate stains proteins and nucleic acid, and Reynolds lead is used to enhance contrast from other metal stains. These metal stains were omitted because they may form small granules or beam-induced punctate densities that obscure cSeNP contrast and assignment. The resulting tomograms are of lower than typical contrast.