  A review of photo-pion experiments on the nucleon in the near threshold
region is presented. Comparisons of the results are made with the predictions
of the low energy theorems of QCD calculated using chiral perturbation theory
(ChPT) which is based on the spontaneous breaking of chiral symmetry as well as
its explicit breaking due to the finite quark masses. As a result of the
vanishing of the threshold amplitudes in the chiral limit, the experiments are
difficult since the cross sections are small. Nevertheless the field has been
brought to a mature stage of accuracy and sensitivity. The accomplishments and
limitations of past experiments are discussed. Future planned experiments at
Mainz and HI$\gamma$S using polarization observables are discussed as a more
rigorous test of theoretical calculations. Emphasis is given to the technical
developments that are required for the HI$\gamma$S facility. It is shown that
future experiments will provide more accurate tests of ChPT and will be
sensitive to isospin breaking dynamics due to the mass difference of the up and
down quarks.
