Fluorescent Liposome DiI incorporates a lipophilic dye inside its membrane, which is insoluble in water. Its fluorescence is easily detected when incorporated into membranes. DiI covers a wide range of excitation and emission wavelengths from 300s to 900s. DiI has fluorescence excitation and emission maxima separated by about 65 nm, facilitating two-color labeling. DiI belongs to the dialkylcarbocyanines family of compounds. They have extremely high extinction coefficients, moderate fluorescence quantum yields and short excited state lifetimes in lipid environments (~1 ns).