  The limits of the Second Law of Thermodynamics, which reigns undisputed in
the macroscopic world, are investigated at the mesoscopic level, corresponding
to spatial dimensions of a few microns. An extremely simple isolated system,
modeled after Callen's adiabatic piston, [1] can, under appropriate conditions,
be described as a self-organizing Brownian motor and shown to exhibit a
perpetuum mobile behavior.
