Free Radical Polymerization (FRP) plays a crucial role in light-based 3D printing due to its rapid curing capability. However, the network inhomogeneities formed during FRP significantly reduce the mechanical properties of the polymer network. In this presentation, I will introduce a novel toughening strategy for 3D-printed elastomers and gels using a uniquely designed crosslinker that enables multivalent supramolecular polymerization. These crosslinkers self-assemble into nanodomains and supramolecular nanofibers within the liquid monomers. During photopolymerization, these predefined nanodomains act as crosslinking points, inducing additional chain entanglement. The resulting polymer network demonstrates enhanced stretchability, strength, fracture toughness, and fatigue threshold, making it applicable to various monomer systems.