In the range of fracture energies between Γ = 20-40 kJ/m 2 , we find double networks of PVA/Alg-Ca 2+ , gelatin/gellan gum-Na + , followed by the single networks of P(MAAm-stat-MAAc), and P(AAm-stat-VIm)-Cu 2+ . It should be mentioned that the hydrogen bond generated hydrogels of reached an elastic modulus of E = 217 MPa, which is one of the highest reported values for tough hydrogels to date. In the range of Γ = 10 -20 kJ/m 2 , almost all classes of interactions are represented (Figure ). Together, these data span a range of stiffnesses up to E = 100 MPa. The exact value of E = 100 MPa is solely achieved through the hydrogen bonding P(NASC) gels. This stiffness is followed by the PAAm/CS-polypyrrole double network (E = 50 MPa), and a dual cross-linked P(AN-stat-AAm) single network (E = 16 MPa). In the range of E = 1-10 MPa with ascending modulus, we find PAAm/CS-Cit 3-and PAAm/κ-Carr-Zr 4+ double networks, , single networks of PVA/SiO 2 nanocomposites, PDMAAm/lignin, a PVA/PAAm double network, an ionic PDMAEA-Q/PNaSS single network, and lastly a PAAm/P(SA-stat-MAAc) SIPN. Overall, the use of double networks may seem favorable to reach mechanical properties for load-bearing applications and indeed, some of the best-performing specimen are double networks. This however, must not be generalized as several single networks are able to reach extreme mechanical properties as well. Additionally, it should be noted that the upper range of mechanical properties (fracture energy and stiffness) are almost exclusively reserved for tough hydrogels, whose water content is below 50%, with few exceptions, such as . This may limit their opportunities in applications, where a high water content is needed.