After 30 years of research, disordered systems remain
one of the great challenges of theoretical physics. This is due
to the existence of multiple minima, or broad distributions of
disorder. The latter render meaningless  standard perturbation theory,
and its most prominent prediction, namely dimensional reduction,
which states that disordered systems behave as pure systems
in two space dimensions less. A theoretical treatment therefore
has to take into account and follow under renormalization the
whole disorder distribution. We review this approach and
discuss a recent application to contact line depinning.