Xylene cyanol is widely used as a tracking dye in molecular biology, particularly in agarose and polyacrylamide gel electrophoresis. It helps monitor the progress of DNA, RNA, or protein migration during electrophoresis due to its distinct blue color. The dye migrates at a rate similar to medium-sized DNA fragments, making it a useful marker for estimating molecular weight. Additionally, it is sometimes used in combination with other dyes, such as bromophenol blue, to provide a broader range of visual reference points. Its application extends to nucleic acid staining and as a component in loading buffers to ensure even sample distribution in gel wells.