Schematic overview of cryogenic sample preparation for SXRF imaging. For single-cell imaging, cells are typically cultured on silicon nitride membranes, and then labeled with fluorophores to image protein distribution in living conditions. Then membranes are rinsed with a solution of ammonium acetate of same pH and osmolarity as the cell-culture medium to remove extracellular elements that would interfere with XRF imaging of intracellular elements (1), excess ammonium acetate is blotted with a filter paper (2) to limit the thickness of the ice layer in the sample, and, finally, the membrane is plunge-frozen into a cryogenic fluid, typically liquid ethane (3).