Energy transfer at the single-molecule scale: including incoherent fluorescence resonant energy transfer (FRET) and coherent electronic energy transfer between the molecular donor and acceptor, plasmon assisted FRET, the coupling of electrically driven quantum emitters with plasmonic waveguides and its potential application in nanoscale optoelectronic integration. By combining with single-molecule electroluminescence/photoluminescence and single-molecule Raman scattering techniques, research will also be extended to the study of the influence of vibronic coupling on the intramolecular optical transition and intermolecular interaction as well as the microscopic mechanism of light-harvesting structures in photosynthesis.