  We examine the response of a quasi-two-dimensional colloidal suspension to a
localized circular driving induced by optical tweezers. This approach, a
microscale version of rheometry, allows us to resolve over three orders of
magnitude in P\'eclet number ($Pe$) and provide a direct observation of a sharp
spatial crossover from far- to near-thermal-equilibrium regions of the
suspension. In particular, particles migrate from high to low $Pe$ regions and
form strongly inhomogeneous steady-state density profiles with an emerging
length scale that does not depend on the particle density and is set by
$Pe\approx1$. We show that the phenomenological two phase fluid constitutive
model is in line with our results.
