The ß-galactosidase substrate, 5-(pentafluorobenzoylamino)fluorescein di-ß-D-galactopyranoside (PFB-FDG) yields the green-fluorescent PFB-F dye (excitation/emission maxima ~492/516 nm), which appears to localize to endosomal and lysosomal compartments when loaded into cells by pinocytosis.