The ZIF-8 crystals were applied to the surface of a holey carbon grid from the methanol suspension essentially as described in our previous work with the ZIF-8 nanocrystals . One key difference here is that we made use of 200 mesh holey carbon grids rather than 300 mesh grids to reduce the number of copper grid bars and increase the usable area of the grid for cryo-FIB milling. Following the evaporation of the methanol, the ZIF-8 grids were loaded into the cryo-FIB/SEM for milling. When the sample was visualized within the FIB/SEM, many ZIF-8 crystals could be seen on the surface (Fig. ). There were several features of the crystals on the grid that were assessed to determine if a crystal was suitable for milling. These included, crystal morphology (single crystal, well-defined shape), located near the center of the grid square away from grid bars, and no other crystals in the path of the ion beam. Crystals that fit these criteria were selected for FIB milling and thin lamella (≈ 150nm thick) were created from these crystals (Fig. ).