  In a baryon-symmetric universe, the baryon asymmetry observed for visible
matter is matched by an equal and opposite asymmetry for dark matter, thereby
closely connecting the number densities of both types of matter. This is a
necessary step towards the goal of explaining the mystery of why the visible
and dark matter densities are observed to be similar. In this talk, a way of
producing such a universe from bubble nucleation during a first-order phase
transition is reviewed. The process is an analog of electroweak baryogenesis.
