  The promise and limitations of studying nuclear structure and reactions using
(e,e'p) reactions are discussed. A(e,e'p)A-1 reactions on complex nuclei are
used to test new relativistic mean-field calculations and their ingredients
such as ground-state wave function, current operators, final-state interactions
and two-body currents, and to assess the limits of single-particle models. For
higher excitations of the residual nuclei, A(e,e'p) reactions reveal only
qualitative features of the reaction mechanism, and their increased usefulness
awaits input from more complex reactions such as A(e,e'X). The (e,e'p)
experiments on few-body nuclei provide essential input to quickly developing
theories for few-body systems, where individual theoretical ingredients can be
studied very selectively. A large data set is needed for this purpose, and
existing or proposed experimental programs are discussed. If hadronic theories
can meet the challenge of consistently describing this body of data at low and
moderate energies, the transition from hadronic to quark-gluon degrees of
freedom could be probed in experiments at higher energies.
