CFSE is a non-fluorescent molecule that easily diffuses across cell membranes

Inside the cell, acetate groups are cleaved by intracellular esterases yielding a fluorescent molecule whose succinimidyl ester group covalently interacts with primary amines of intracellular proteins. CFSE is compatible with standard intracellular staining protocols using aldehyde fixation and saponin-based permeabilization. CFSE is widely used to track cell division and to monitor cell migration in vivo. CFSE can be detected using standard fluorescein filter sets by fluorescence microscopy or flow cytometry.