Resonance photo and electroproduction as a probe of QCD

Analogies have been drawn between QCD where quarks build up hadrons, which in turn build up nuclei, and QED where electrons build up atoms, which in turn build up molecules. The author discusses the issue of creating a quark theory of the nucleus in QCD by analogy with the way electrons build up molecules in QED. In QED the first step has been achieved, namely understanding atoms in terms of their electronic structure, but molecular structure in QED is only understood in rather simple cases. In QCD the situation is even worse, in that researchers haven't even achieved the first step, namely in understanding how hadrons are built from quarks