  In metallic samples of small enough size and sufficiently strong
momentum-conserving scattering, the viscosity of the electron gas can become
the dominant process governing transport. In this regime, momentum is a
long-lived quantity whose evolution is described by an emergent hydrodynamical
theory. Furthermore, breaking time-reversal symmetry leads to the appearance of
an odd component to the viscosity called the Hall viscosity, which has
attracted considerable attention recently due to its quantized nature in gapped
systems but still eludes experimental confirmation. Based on microscopic
calculations, we discuss how to measure the effects of both the even and odd
components of the viscosity using hydrodynamic electronic transport in
mesoscopic samples under applied magnetic fields.
