PEGylated proteins (PEG, polyethylene glycol) are often viewed as representatives of protein–polymer conjugates, largely due to their success in therapeutic applications.^1,2  However, the field has progressed significantly since the first reports of these hybrid bioconjugates in the late 1970s. Nowadays, protein–polymer conjugates have advanced well beyond simple protein PEGylation and various synthetic polymers and biomacromolecules have been combined.^3,4  This progress is associated with the parallel development of new chemical methods and recombinant technologies over the last decades, which made it possible to incorporate both natural and synthetic polymers to greatly expand the library of protein–(bio)polymer hybrids such as protein–dendrimer,^5,6  protein–protein^7,8  and protein–deoxyribonucleic acid^9,10  complexes. Through the combination of proteins with macromolecules, the physical properties, stability and functionality of the resultant biohybrids could be customized for various applications in biomedicine and biotechnology.^2,11–13  Clearly, the merger of different classes of macromolecules has offered possibilities beyond post-translational modification (PTM) processes in Nature, where non-amino acid entities are incorporated into proteins to modulate their stability, physicochemical properties, interaction propensities, or localization within cellular compartments.^14,15  However, it is also evident in Nature that higher-order protein nanostructures and networks, through controlled self-assembly, are essential to many important processes supporting life.¹⁶  Intuitively, the next step in materials design will be to control the three-dimensional (3D) architecture of protein–(bio)polymer conjugates, which could have significant impact on their functions and, consequently, the resultant unique features can be exploited for various technological applications (Figure 9.1).