  The merits and limitations of the Nambu--Jona-Lasinio model as a model for
strong interactions at nonzero density are critically discussed. We present
several examples, demonstrating that, while in general the results should not
be trusted quantitatively, the NJL model is a powerful theoretical tool for
getting new insights and ideas about the QCD phase diagram and the dense-matter
equation of state.

High Energy Physics - Phenomenology;Nuclear Theory