The styryl dye FM 4-64 has been reported to selectively stain yeast vacuolar membranes with red fluorescence (excitation/emission maxima ∼515/640 nm). This lipophilic dye is an important tool for visualizing vacuolar organelle morphology and dynamics, for studying the endocytic pathway and for screening and characterizing yeast endocytosis mutants. FM 4-64 is also available in special packaging with 10 vials of 100 μg each (T-13320).