  Exclusive two-pion production near threshold in the collision of a highly
virtual photon with a real one offers a new possibility to unravel the partonic
content of hadrons. We explain the dynamics of this regime, i.e. the separation
of the amplitude in terms of partonic diagrams computable in QCD perturbation
theory and generalized distribution amplitudes, which are nonperturbative
functions describing the exclusive transition of a parton pair into two
hadrons. The same quantities also appear in gamma* N -> pi pi N in the
kinematical regime where the momentum transfer of the nucleon and the invariant
mass of the pion pair are both small; this allows to extend the QCD analysis of
exclusive rho electroproduction outside the resonance region of the two
produced pions.
