The green fluorescent, lipophilic carbocyanine DiOC₁₈(3) is widely used as a lipophilic tracer. It is weakly fluorescent in water, but highly fluorescent and quite photostable when incorporated into membranes. It has an extremely high extinction coefficient and short excited-state lifetimes (∼1 nanosecond) in lipid environments. Once applied to cells, the dye diffuses laterally within the plasma membrane.

We recommend preparing stock solutions of lipophilic tracers in dimethyl formamide (DMF), dimethylsulfoxide (DMSO), or ethanol at 1 to 2.5 mg/mL. DMF is preferable to ethanol as a solvent for DiO.