  Double deeply virtual Compton scattering (DDVCS) is a very precise tool for
the nucleon tomography. Its measurement requires high luminosity electron beams
and precise dedicated detectors, since its amplitude is quite small in the
interesting kinematical domain where collinear QCD factorization allows the
extraction of quark and gluon generalized parton distributions (GPDs). We
analyze the prospects for its study in the JLab energy domain as well as in
higher energy electron-ion colliders. Our results are very encouraging for
various observables both with an unpolarized and polarized lepton beam. Using
various realistic models for GPDs, we demonstrate that DDVCS measurements are
indeed very sensitive to their behaviour. Implementing our lowest order
cross-section formulae in the EpIC Monte Carlo generator, we estimate the
expected number of interesting events.
