This module enables a mechanism which describes an energy transfer between two chromophores, typically fluorescent proteins. Upon excitation with light of suitable wavelength a donor chromophore, then in its electronic excited state, can transfer energy to an acceptor chromophore. The efficiency of this energy transfer depends on the distance between the two molecules. This makes FRET an indicator for even very small changes in the distance between two molecules.

When using confocal or super resolution techniques, FRET is typically used to determine whether two fluorophores are within a certain distance of each other and whether this distance changes due to external or internal influences.