  We review the theory of hadronic atoms in QCD + QED, based on a
non-relativistic effective Lagrangian framework. We first provide an
introduction to the theory, and then describe several applications:
meson-meson, meson-nucleon atoms and meson-deuteron compounds. Finally, we
compare the quantum field theory framework used here with the traditional
approach, which is based on quantum-mechanical potential scattering.
