Förster resonance energy transfer - (a method for measuring distances at the nanoscale)

Förster resonance energy transfer (FRET) is a technique used to measure very small distances—on the order of nanometers—between two molecules. It involves a donor molecule that, when excited by light, can transfer its energy non-radiatively to an acceptor molecule nearby. This transfer occurs only if the molecules are very close and properly aligned, making FRET a sensitive "molecular ruler." By measuring how efficiently energy transfers from donor to acceptor, scientists can determine the distance between molecules, helping to study structures and interactions at the molecular scale.