The results of experiments at hadron colliders probing the
structure of the pomeron through hard diffraction are reviewed.  Some results
on deep inelastic scattering obtained at HERA are also discussed and placed
in perspective.  By using a properly normalized pomeron flux factor in single
diffraction dissociation, as dictated by unitarity, the pomeron emerges as a
combination of valence quark and gluon color singlets in a ratio suggested by
asymptopia.