  Improved measurements of the proton's structure are now possible thanks to
significant technical advances that allow us to probe the proton with polarized
photons. These measurements have shown that the proton is not as simple as
previously believed: quark orbital angular momentum and relativistic effects
play an important role and the spatial distribution of charge and magnetization
do not simply mimic the spatial distribution of the quarks. Even more recently,
the large scale structure and size of the proton have been examined more
carefully, and a significant discrepancy has been observed between the charge
radius of the proton as measured in the Lamb shift of muonic hydrogen and
measurements using the electron-proton interaction.
