Quantum electrodynamics (QED) is the relativistic quantum field theory of electrodynamics. QED was developed by a number of physicists, beginning in the late 1920s. It basically describes how light and matter interact. QED mathematically describes all phenomena involving electrically charged particles interacting by means of exchange of photons. Physicist Richard Feynman has called it "the jewel of physics" for its extremely accurate predictions of quantities like the anomalous magnetic moment of the electron, and the Lamb shift of the energy levels of hydrogen.