  We show systematically that a steady-state ensemble of mesoscopic inclusions
of a solute-rich fluid can emerge in liquid solutions well outside the region
of stability of the solute-rich phase. Unanticipated by conventional
treatments, this type of reversible aggregation nonetheless can take place if
the solute molecules bind transiently with each other to form long-lived
complexes. The binding causes kinetic stabilization of inclusions of the
solute-rich phase---within a substantial size range---so as to render the
critical size for nucleation of the inclusions finite. Individual droplets
nucleate and grow until they become mechanically unstable because of a
concomitant drop in the internal pressure, the latter drop caused by the
thermodynamic metastability of the solute-rich phase. At the same time, the
{\em ensemble} of the droplets is steady-state on long times. In a freshly
prepared solution, the ensemble is predicted to evolve similarly to the
conventional Ostwald ripening, during which larger droplets grow at the expense
of smaller droplets. The present mechanism is proposed to underlie the puzzling
mesoscopic clusters observed in solutions of proteins and other molecules.
