It has now become difficult to be a generalist even in theoretic physics. You could be a particle theorist, cosmologist, or condensed matter theorist, but rarely all three! Even in particle theory, you would specialize in QCD, or electroweak theory, and in QCD you might specialize in confinement, lattice QCD, or quark-gluon plasma. Nature, however, does not know about our subdivisions, and exhibits phenomena that cut across all our specialities.
from Superfluid Universe by K. Huang