Sulfo Cy5.5-N3 is a fluorescent dye known as a Sulfo Cy5.5 azide. This compound can be employed in cell imaging via click chemistry. It contains an azide group, allowing it to participate in copper-catalyzed azide-alkyne cycloaddition reactions (CuAAC) with molecules containing alkyne groups. Additionally, it can engage in strain-promoted azide-alkyne cycloaddition reactions (SPAAC) with molecules that have DBCO or BCN groups.