DiI is a lipophilic membrane stain that diffuses laterally to stain the entire cell. It is weakly fluorescent until incorporated into membranes. This orange/red-fluorescent dye, which is spectrally similar to tetramethylrhodamine, is often used as a long-term tracer for neuronal and other cells. DiI is also available as a solution (Cat. No. V-22885), as a paste (Cat. No. N-22880) or as a solid (Cat. No. D-282).

Prepare stock solutions of lipophilic tracers in dimethyl formamide (DMF), dimethylsulfoxide (DMSO), or ethanol at 1 to 2.5 mg/mL.