Dihydrofluorescein diacetate is widely used as a fluorescent probe to detect reactive oxygen species (ROS) in biological systems. Once inside cells, it is deacetylated by esterases to form dihydrofluorescein, which is non-fluorescent. Upon oxidation by ROS, it converts to fluorescein, emitting green fluorescence that can be measured using fluorescence microscopy or flow cytometry. This makes it a valuable tool in studying oxidative stress, cellular damage, and the role of ROS in various diseases, such as cancer, neurodegenerative disorders, and inflammation. Its sensitivity and ease of use have made it a popular choice in research focused on understanding cellular redox dynamics.