  In systems possessing a spatial or dynamical symmetry breaking thermal
Brownian motion combined with unbiased, non-equilibrium noise gives rise to a
channelling of chance that can be used to exercise control over systems at the
micro- and even on the nano-scale. This theme is known as ``Brownian motor''
concept. The constructive role of (the generally overdamped) Brownian motion is
exemplified for a noise-induced transport of particles within various set-ups.
We first present the working principles and characteristics with a
proof-of-principle device, a diffusive temperature Brownian motor. Next, we
consider very recent applications based on the phenomenon of signal mixing. The
latter is particularly simple to implement experimentally in order to optimize
and selectively control a rich variety of directed transport behaviors. The
subtleties and also the potential for Brownian motors operating in the quantum
regime are outlined and some state-of-the-art applications, together with
future roadways, are presented.
