Fluorescence Resonance Energy Transfer (FRET) is a powerful technique used to study the interactions and distances between two molecules, typically within the range of 1-10 nm, by transferring energy from a donor fluorophore to an acceptor fluorophore without the emission of a photon. This process is highly sensitive to the distance between the donor and acceptor, making FRET an invaluable tool in molecular biology, biochemistry, and biophysics for understanding molecular dynamics, protein-protein interactions, and conformational changes.