  There is much speculation and a modest amount of evidence that certain mesons
might form quasi-bound states with nuclei to produce really exotic states of
matter. For this to be a practical possibility, the interaction between the
meson and nucleons at low energies must be strong and attractive and the
production rates "healthy". The conditions for this are surveyed for the light
mesons. How this might lead to quasi-bound states is then discussed in a few
typical cases.
