Polyelectrolytes in the presence of oppositely charged small colloids may exhibit soluble complex formation or precipitation, but an intermediate state of hydration involves the formation of a macroion-rich second liquid phase. These dense, optically clear and often viscous coacervates exhibit unusual rheological and transport properties, in particular colloid translational diffusivities that are remarkably large given the large macroscopic viscosities. For coacervates of a protein (BSA) with polycations, dynamic light scattering and neutron scattering both provide evidence of mesophase separation on the scale of a few hundred nm, a phenomenon also consistent with the results from a number of other techniques (Cryo-TEM, rheology, FRAP, PFG-NMR and FCS). Marked differences between protein-polyelectrolyte coacervates and micelle-polyelectrolyte coacervates correspond to different types of mesophases. In the case of polyelectrolyte-protein coacervates, coacervate properties and stability are strongly influenced when chitosan replaces PDADMAC, a synthetic polycation with the same structural charge density but smaller persistence length. For chitosan-BSA coacervates, SANS clearly indicated the presence of a fractal structure in the range q<0.06 (1/nm). Possible origins of mesophase structures will be discussed.