  We examine hydrodynamics from the perspective of an effective field theory.
The microscopic scale in this case is the thermalization scale, and the
macroscopic scale is the gradient, with thermal fluctuations playing the role
of $\hbar$. We argue that this method can be applied both, to consistently
include thermal fluctuations in the theory, and to extend hydrodynamics to
systems whose microscopic structure is non-trivial. For the latter, we discuss
the case of spin polarization and gauge theories.
