||Nile Red is an uncharged, hydrophobic, photostable molecule that strongly fluoresces bright red in hydrophobic environments. This lipophilic stain is commonly used for the detection of intracellular lipid droplets by fluorescence microscopy and flow cytofluorometry. Nile Red has been shown to detect the exposure or formation of new hydrophobic surfaces induced by ligand binding to calmodulin, oligomerization of melittin, or unfolding of ovalbumin during early thermal denaturation. This product has been employed to stain cell structures, as well as to visualize and localize colloidal drug carriers. Nile Red"s fluorescence is unaffected between pH 4.5 and 8.5 and may be used in dilute concentrations to investigate hydrophobic protein sites.