Throughout this review, we have seen that innovative cross-linking strategies often give rise to a broad span of mechanical properties, producing-for the first time-fracture energies and elastic moduli that exceed Γ = 100 kJ/m 2 and E = 100 MPa, respectively (this was enabled specifically through PVA microcrystallization, hydrogen bonding and composite materials). Double networks combining covalent and non-covalent networks often managed to reconciliate good fracture energies with high stretchabilities (>1000%), however, their stiffness remained limited. Metalligand interactions have shown to effectively improve stiffness (E = 10-20 MPa), while their water content is generally lower than many double networks. A similar trend is observed for polyampholytes where a sufficiently high concentration is needed to enable gelation via the ionic interactions along with enhanced (fracture) mechanical properties. Some of the most efficient networks combine multiple interactions, such as PVA microcrystallization, metal-ligand interactions, or hydrogen bonding, in a double network architecture. In the category of hydrogen bonding, a wide range of stiffnesses and fracture energies is observerd that was mainly driven by the introduction of new innovative monomers capable of strongly interacting with each other. Microphase separation via micellization or hydrophobic interactions often enhanced stiffness, while the water content varied at large. Composite materials offered the widest range of properties, reaching new heights in fracture energy and stiffness, yet often the most stiff samples suffered greatly in terms of stretchability. The literature examples in the category of self-assembly are still few in number, yet selected examples using protein folding or host-guest interactions showed great potential for tough hydrogels. Especially networks with unique topologies (such as slide-rings) managed to combine outstanding stretchabilities with good fracture energies and we believe such topologies merit further exploration. Overall, the discussed literature on tough hydrogels gave key insights into structure-property relationships and illustrated, how individual parameters, such as fracture energy (or fracture strain) often come at the expense of others (e.g., stiffness). The careful adjustment of parameters remains therefore critical to match physicochemical and (fracture) mechanical properties of tough hydrogels to those of a given targeted environment (e.g., various tissues).