  Virtual photons have proven to be very efficient probes of the hadronic
structure, mostly through deep inelastic scattering and related processes. The
advent of high luminosity lepton beams has allowed to enlarge the studied
processes to hard exclusive reactions, such as deeply virtual Compton
scattering and the electroproduction of mesons. We discuss theoretical progress
which has lately been quite remarkable in this domain and first much
encouraging experimental data.
