Used primarily as a fluorescent tracer in biological and medical applications, this compound is valued for its ability to penetrate cell membranes due to its lipophilic propionate groups. Once inside cells, esterases cleave the propionate moieties, converting it into the fluorescent fluorescein, which becomes trapped intracellularly. This property makes it ideal for cell viability assays, cell tracking in co-culture systems, and monitoring cell proliferation and migration in research. It is also employed in flow cytometry and fluorescence microscopy to label and visualize live cells. Additionally, it finds use in environmental studies to trace fluid flow and detect leaks in complex systems due to its strong, visible fluorescence under UV or blue light.