This Standard Operating Procedure (SOP) is based on the Human Islet Phenotyping Program of the IIDP Immunofluorescence Staining Procedure. This SOP provides the HIPP procedure for immunofluorescent staining, imaging, and analysis of islet preparations. This SOP defines the assay method used by the Human Islet Phenotyping Program (HIPP) for quantitative and qualitative determination of the Purified Human Pancreatic Islet product, post-shipment, manufactured for use in the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)-sponsored research in the Integrated Islet Distribution Program (IIDP).