Nile red is used to localize and quantitate lipids, particularly neutral lipid droplets within cells. Nile red is almost nonfluorescent in water and other polar solvents but undergoes fluorescence enhancement and large absorption and emission blue shifts in nonpolar environments.    Dark red solid soluble in DMF and DMSO  Abs/em=552nm /636 nm (methanol)  Store at 4°C and protect from light  C20H18N2O2M  MWt: 318.37  [7385-67-3]