  We give an elementary and pedagogical review of the phase diagrams which are
possible in Quantum ChromoDynamics (QCD). Currently, the emphasis is upon the
appearance of a critical endpoint, where disordered and ordered phases meet. In
many models, though, a Lifshitz point also arises. At a Lifshitz point, three
phases meet: disordered, ordered, and one where spatially inhomogeneous phases
arise. At the level of mean field theory, the appearance of a Lifshitz point
does not dramatically affect the phase diagram. We argue, however, that
fluctuations about the Lifshitz point are very strong in the infrared, and
significantly alter the phase diagram. We discuss at length the analogy to
inhomogenous polymers, where the Lifshitz regime produces a bicontinuous
microemulsion. We briefly mention the possible relevance to the phase diagram
of QCD.
