To compare lateral resolution of the NanoSIMS-HR to a NanoSIMS 50L, measurements were made on an aluminum sample with high silicon content ("Al-Si sample") because the Si forms Al-free domains that provide sharp chemical contrast for these measurements. The sample was polished with diamond paste down to 0.1 micron (Buehler) and then colloidal silica (Buehler). Additional imaging was performed with biological samples, detailed below.