  Lift forces are widespread in hydrodynamics. These are typically observed for
big and fast objects, and are often associated with a combination of fluid
inertia (i.e. large Reynolds numbers) and specific symmetry-breaking
mechanisms. In contrast, the properties of viscosity-dominated (i.e. low
Reynolds numbers) flows make it more difficult for such lift forces to emerge.
However, the inclusion of boundary effects qualitatively changes this picture.
Indeed, in the context of soft and biological matter, recent studies have
revealed the emergence of novel lift forces generated by boundary softness,
flow gradients and/or surface charges. The aim of the present review is to
gather and analyse this corpus of literature, in order to identify and unify
the questioning within the associated communities, and pave the way towards
future research.
