  Describing hadronic structure is one of the most intriguing problems in
physics. In this respect, generalized parton distributions (GPDs) constitute an
outstanding tool, allowing to draw "three dimensional pictures" of hadron's
inside. Starting from contemporary models for pion's GPDs fulfilling all
constraints imposed by QCD, we compute Compton form factors (CFFs) of pions
subjected to deeply virtual Compton scattering. We show the behaviour of CFFs
to be gluon-dominated at EIC's kinematics. Finally we evaluate lepton-beam-spin
asymmetries in the Sullivan process, demonstrating the existence of such and
thus triggering optimism about the possibility of probing pion's 3D structure
at electron-ion colliders.
