Using biologically-inspired approaches, proteins can be engineered to make functional biomaterials. Some polypeptides can undergo a liquid-liquid phase separation, either simple (1 component) or complex (2+ components), forming a dense, protein-rich phase that can then be used for purposes like injectable biomaterials or biosorbents. The properties of the dense phase can be tuned through a variety of different methods, and a fundamental understanding of the parameter space is critical for engineering better biomaterials. Beyond coacervation, we also seek to engineer living biomaterials.