  Osmosis is a universal phenomenon occurring in a broad variety of processes
and fields. It is the archetype of entropic forces, both trivial in its
fundamental expression - the van 't Hoff perfect gas law - and highly subtle in
its physical roots. While osmosis is intimately linked with transport across
membranes, it also manifests itself as an interfacial transport phenomenon: the
so-called diffusio-osmosis and -phoresis, whose consequences are presently
actively explored for example for the manipulation of colloidal suspensions or
the development of active colloidal swimmers. Here we give a global and
unifying view of the phenomenon of osmosis and its consequences with a
multi-disciplinary perspective. Pushing the fundamental understanding of
osmosis allows to propose new perspectives for different fields and we
highlight a number of examples along these lines, for example introducing the
concepts of osmotic diodes, active separation and far from equilibrium osmosis,
raising in turn fundamental questions in the thermodynamics of separation. The
applications of osmosis are also obviously considerable and span very diverse
fields. Here we discuss a selection of phenomena and applications where osmosis
shows great promises: osmotic phenomena in membrane science (with recent
developments in separation, desalination, reverse osmosis for water
purification thanks in particular to the emergence of new nanomaterials);
applications in biology and health (in particular discussing the kidney
filtration process); osmosis and energy harvesting (in particular, osmotic
power and blue energy as well as capacitive mixing); applications in detergency
and cleaning, as well as for oil recovery in porous media.
