Attempt to describe all fundamental interactions between elementary particles in terms of a single theoretical framework (a "theory of everything") based on quantum field theory .
So far, the weak force and the electromagnetic force have been successfully united in electroweak theory , and the strong force is described by a similar quantum field theory called quantum chromodynamics . However, attempts to unite the strong and electroweak theories in a grand unified theory have failed, as have attempts at a self-consistent quantum field theory of gravitation .