  Generalized Parton Distributions (GPDs) offer a new way to access the quark
and gluon nucleon structure. We review recent progress in this domain,
emphasizing the need to supplement the experimental study of deeply virtual
Compton scattering by its crossed version, timelike Compton scattering. We also
describe the extension of the GPD concept to three quark operators and the
relevance of their nucleon to meson matrix elements, namely the transition
distribution amplitudes (TDAs) which factorize in backward meson
electroproduction and related processes. We discuss the main properties of the
TDAs. \
