[en] Understanding the dynamics of non-perturbative QCD (the physics of quark and gluon interactions at large coupling) is one of the most challenging problems of modern physics. The two phenomena of quark confinement, which binds quarks permanently inside hadrons, and the dynamical breaking of chiral symmetry, which gives us pion physics and more massive constituent quarks of low energy QCD, define the interface of nuclear and particle physics. The Electron Laboratory for Europe project - ELFE - is the European machine initiative proposed as the optimum experimental tool to study this ''Confinement Physics'', which is virgin territory for both particle and nuclear physicists. Until recently, lack of data in the confinement domain had led to slow theoretical progress in understanding the quark structure of nuclear and hadronic matter. This situation has improved considerably, with new discoveries in high energy deep inelastic scattering experiments together with important advances in large acceptance detector technology and continuous electron beams at low energies. At high energies, the CERN muon beam experiments in deep inelastic scattering (probing the remote interior of nucleons) opened an exciting new window on nucleon structure with the discovery of three unexpected effects: the EMC (European Muon Collaboration) nuclear and spin effects, and the observation of a surprisingly large difference between the the number of anti-up and anti-down quarks in nucleons. In 1983, the EMC nuclear effect showed that the quark structure of the free nucleon is modified in the nuclear environment. The EMC spin effect (or proton spin problem) is the discovery that it looks as though quark spin contributes only 22% of that of the nucleon (July 1994, page 19)