Studies of the endomembrane system often involve the use of a protein that can emit a green fluorescence (glow). A researcher wants to make a video of cell behavior, so she initially tags the outer nuclear envelope of a cell with the fluorescent tag and records for several hours. later, she sees that the tag is part of a secretory vesicle. The ability to stain protein molecules with a fluorescent dye would most clearly allow researchers to go beyond what they could previously detect with a microscope by allowing them to track the movement of the protein in the cell. This will give an insight on the organelles that are involved in the process, signalling pathways, receptors involved in the process, etc.