Samples were transferred to the OrbiSIMS instrument under liquid nitrogen after TEM imaging for molecular depth profiling under cryogenic conditions (-170°C). An Ar3000 + gas cluster source was used both as a primary ion analysis and depth profiling beam. These measurements were undertaken on an ensemble of particles simultaneously over a 400 µm x 400 µm area since the lateral resolution of the analysis beam is not sufficient to resolve individual LNPs. Secondary ion assignments were guided by the individual component reference spectra (Figure ), although in the case of this LNP formulation, all observed fragments were unique to one component, and definitively linked to the lipid molecular structures.