Used primarily as a fluorescent dye in biological staining and imaging applications. It labels cell membranes due to its lipophilic nature, allowing visualization of membrane structure and dynamics in live or fixed cells. Commonly employed in fluorescence microscopy and cell tracing studies, it integrates into lipid bilayers and emits strong fluorescence when excited by appropriate light, enabling researchers to track cell movement, fusion, and morphology over time. Also utilized in neuroscience for neuronal pathway tracing because it can diffuse laterally along membranes and highlight cellular connections.