  A brief review of unconventional superconductivity is given, stretching from
the halcyon days of helium-3 to the modern world of Majorana fermions. Along
the way, we will encounter such strange beasts as heavy fermion
superconductors, cuprates, and their iron-based cousins. Emphasis will be put
on the fact that in almost all cases, an accepted microscopic theory has yet to
emerge. This is attributed to the difficulty of constructing a theory of
superconductivity outside the Migdal-Eliashberg framework.
