DiO is widely used as a fluorescent membrane dye in biological and cellular imaging. It readily incorporates into cell membranes due to its lipophilic properties, making it ideal for labeling and tracing cell morphology and membrane dynamics. It is commonly applied in cell lineage studies, cell migration assays, and fusion experiments due to its bright fluorescence and photostability. DiO is also used for long-term cell tracking in vivo and in vitro, as it persists in membranes through cell divisions. Additionally, it serves as a neuronal tracer in developmental neuroscience to map axonal pathways. Its compatibility with live-cell imaging and minimal toxicity allow for real-time visualization without significantly disrupting cell function.