  In this non-specialist review I look at how weak lensing can provide
information on the dark sector of the Universe. The review concentrates on what
can be learned about Dark Matter, Dark Energy and Dark Gravity, and why. On
Dark Matter, results on the confrontation of theoretical profiles with
observation are reviewed, and measurements of neutrino masses discussed. On
Dark Energy, the interest is whether this could be Einstein's cosmological
constant, and prospects for high-precision studies of the equation of state are
considered. On Dark Gravity, we consider the exciting prospects for future weak
lensing surveys to distinguish General Relativity from extra-dimensional or
other gravity theories.
