This Standard Operating Procedure (SOP) is adapted from the Viability SOP from the Clinical Islet Transplant Consortium Protocol and the Integrated Islet Distribution Program (IIDP) for Distribution Centers. This SOP provides the Human Islet Phenotyping Program (HIPP) procedures for Fluorescein Diacetate (FDA) and Propidium Iodide (PI) staining and imaging of islet preparation for qualitative viability assessment. 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).