The success of the nuclear shell model was a pleasant surprise. This pointed toward the possibility that nucleons can be regarded as moving approximately in an average nuclear mean field. Indeed, it has now been established that important overall nuclear properties, such as saturation, can be described by a relativistic field theory. Nuclear saturation means that in the limit of large mass number, the energy per particle and the average density approach a constant. In the nuclear mean field theory, nucleons are generally regarded as points exchanging Yukawa mesons, and the finite nucleon size is neglected or simulated by relativity. An improvement over this is the quark-meson coupling model.