FM1-43 is widely used as a fluorescent dye to study cellular membrane dynamics, particularly in the field of neuroscience and cell biology. It is commonly employed to visualize and monitor exocytosis and endocytosis in real time due to its ability to label cell membranes selectively. When membranes undergo fusion or recycling, FM1-43 incorporates into the lipid bilayer and exhibits strong fluorescence upon binding, making it ideal for tracking synaptic vesicle recycling in neurons. Researchers use FM1-43 in live-cell imaging experiments to observe the kinetics of vesicle release and retrieval at nerve terminals. It is also applied in studies of secretory cells such as chromaffin cells and pancreatic beta cells to examine how vesicles are recycled after stimulation. Due to its high sensitivity and low background fluorescence in aqueous environments, FM1-43 allows for precise detection of membrane trafficking events using fluorescence microscopy. Additionally, it is used in combination with other dyes or optogenetic tools to perform multiparametric analysis of cellular activity.