N-(1-Pyrenyl)maleimide is widely used as a fluorescent labeling reagent in biochemical and biophysical research. Its pyrene moiety provides strong fluorescence, making it valuable for tagging proteins, peptides, and other biomolecules to study their structure, dynamics, and interactions. It is particularly useful in Förster resonance energy transfer (FRET) studies due to its long fluorescence lifetime and excimer formation capabilities. Additionally, it is employed in the development of biosensors and imaging probes, enabling the visualization of cellular processes and molecular pathways. Its reactivity with thiol groups allows for selective conjugation to cysteine residues in proteins, facilitating site-specific labeling.