I read Feynman's quantum electrodynamics, but I do not clearly understand, where quantum mechanics enter. So if clasicaly force in electrostatic field equals F = e^2 /4 pi epsilon 0 r^2. What happens, when quanum mechanics is included. I think that for elementary principle we do need renormalization and screening of charge and so one. We need only F = function of h? Jump from classical gravitational field to quantum gravitational field is unknown, but jump from classical electrostatic field to quantum electrostatic field is known. It is possible to say that electrostatic force is consequence of virtual photons, but some say that virtual photons are only mathematical help in approximative area and they are not real.