Fluorescent Liposome DiR incorporates a lipophilic dye inside its membrane, which is insoluble in water. Its fluorescence is easily detected when incorporated into membranes. DiR covers a wide range of excitation and emission wavelengths from 300s to 900s. DiR belongs to the dialkylcarbocyanines family of compounds. The spectral properties of the dialkylcarbocyanines are largely independent of the lengths of the alkyl chains, which are determined by the heteroatoms in the terminal ring systems and the length of the connecting bridge. They have extremely high extinction coefficients, moderate fluorescence quantum yields and short excited state lifetimes in lipid environments (~1 ns).