Recently, it has been recognized that cells utilize coacervation and liquid-liquid phase separation to compartmentalize and regulate their matter, and to create microenvironments akin to bionanoreactors for catalyzing chemical reactions or protein folding. This recognition sparked a new interest in the old phenomenon of complex coacervation. Furthermore, it has been demonstrated that coacervates made of synthetic polyelectrolytes can be used to sequestrate proteins, similar to the membraneless organelles which can selectively encapsulate proteins from cytoplasm.