Although hydrogels based on polyampholytes (polymers with both positive and negative charges) have been known since the early 1950s, it was not until 2013 when they were used to prepare tough hydrogels. Since then, Gong and co-workers have significantly contributed to polyampholyte hydrogels, where ionic attractions between oppositely charged comonomers led to tough, mechanically robust materials (Figure ). Several outstanding examples made use of sodium p-styrenesulfonate comonomers (NaSS). The first work combined the negatively charged monomer with positively charged acryloyloxethyltrimethylammonium chloride (DMAEA-Q). With a water content of 43%, these tough single networks achieved elastic modulus and fracture energy of E = 7.9 MPa and Γ = 11.8 kJ/m 2 , respectively. Changing the positively charged monomer to 3-(methacryloylamino)propyltrimethylammonium chloride (MPTC) had little effect onto the overall mechanical properties, unlike the addition of various PEG substrates as osmolytes. In the presence of PEG in different concentrations, the hydrogels underwent phase transition from the viscoelastic to the glassy state. For instance, using 30 wt% of PEG for the gel sample (overall water content of 39%), an elastic modulus and a fracture energy of E = 12.9 MPa and Γ = 7.3 kJ/m 2 were obtained, respectively. The interactions between ionic groups is generally based on charge balance and therefore requires each positively charged residue to be compensated by a negatively charged one. In a recent example, Gong and co-workers presented a dual cross-linked network (covalent & ionic), where postively charged monomers are combined with sulfobetaine methacrylate. The resulting tough gels had a water content of 70% and while they showed good fracture properties (Γ = 12 kJ/m 2 ), the stiffness was determined to be rather low (E = 1.7 kPa). The latter could be a result of charge imbalances through use of the zwitterionic sulfobetaine monomer, which natively carries both charges in the first place.