5(6)-Carboxyfluorescein N-succinimidyl ester (Cat No.: M016838) is a fluorescent dye commonly used for long-term cell tracking and proliferation studies. It passively diffuses into cells and covalently binds to intracellular amines via its succinimidyl ester group, resulting in stable, fluorescent labeling. Upon cell division, fluorescence intensity is halved, allowing quantification of proliferation. CFSE exhibits high photostability and bright green fluorescence (excitation ~492 nm, emission ~517 nm), making it ideal for flow cytometry, confocal microscopy, and other fluorescence-based cellular assays.