Fluorescence lifetime is a critical parameter used in the field of fluorescence spectroscopy to characterize the decay time of the emission of a fluorescent molecule after excitation. It is a measure of how long a molecule remains in its excited state before emitting a photon. Fluorescence lifetime measurements can provide valuable information about the environment, interactions, and dynamics of fluorophores in biological systems, materials, and chemical compounds. This parameter is widely used in various applications, such as molecular biology, biochemistry, medical diagnostics, and material science, to study protein-protein interactions, protein-ligand binding, cell imaging, and drug discovery.