[93] Analogous to proteins, well-hydrated anions (e.g., SO 2- 4 and CO 2- 3 ) can polarize the water molecules in the hydration shell of synthetic polymers, destabilizing their surrounding hydrogen bonding network. When a hydrogel expe-riences salting-out, polymer chains partially collapse rather than precipitate, resulting in microphase separated (sometimes crystalline) polymer clusters that act as physical crosslinks within the network. Traditionally, microphase separation is associated with block copolymers that consist of at least two immiscible blocks (often hydrophilic and hydrophobic). In solution, microphase separation can be facilitated by adding surfactants that promote the micellization of hydrophobic entities in an aqueous bulk phase. Consequently, micellized hydrogels can be obtained through polymerization when (i) micelles are loaded with hydrophobic monomers and (ii) sufficient amounts of hydrophilic monomers are present in the aqueous bulk phase (Figure ). Among the hydrophobic monomers, (meth)acrylates with aliphatic alkyl groups (e.g., stearyl, lauryl) have been frequently selected. The interaction between these hydrophobic alkyl groups is on the order of 0.37 kcal/mol per -CH 2 -unit and therefore, can exert significant impact, once many thousands of molecules assemble. In the resulting hydrogel, the polymerized micellar aggregates can act as dynamic cross-links as they deform and re-assemble under loads providing the gel with viscoelastic properties. Micellization has therefore become a potent mechanism of energy dissipation contributing to the development of tough hydrogels. Being well aware of the fact that micellization is also a result of hydrophobic interactions, we nonetheless distinguish between both categories to enable a clear arrangement of the data on tough hydrogels discussed in this review. Hence, active pre-assembly of polymerizable building blocks and surfactants prior to their polymerization is categorized as micellization, while microphase separation in the absence of surfactants driven solely by hydrophobic interactions is classified as such (Figure ). Respective examples discussed in this review often involve film-casting and solvent-exchange methods. Firstly, block copolymers are homogeneously dissolved in an organic solvent followed by casting a polymer film in a mold. Upon drying of the film, hydrophobic interactions drive microphase separation of the block copolymers. When the dried film is immersed in water, residual organic solvents are removed giving rise to the final microphaseseparated tough hydrogel. Selected systems use hydrophobic monomers, such as butyl methacrylate (BuMA), octyl methacrylate (OMA), , stearyl acrylate (SA), 2-(N-ethylperfluorooctanesulfonamido)ethyl acrylate (FOSA), phenyl acrylate (PhA), acrylonitrile (AN), among other formulations. Composite materials generally consist of individual constituents, each possessing distinct properties, which combined give rise to a new material with superior properties. Nanocomposite hydrogels comprise a bulk phase of water-swollen polymer chains and at least one other phase of a solid materials with nanoscale morphology (Figure ). To form cross-links that stabilize the network, poly-mer chains are either covalently or physically bound to the surface of the embedded nanostructures. In the first case, the nanoparticle surface is modified with chemical ligands that can either be copolymerized (grafting from) or reacted with/replaced by functional polymers forming stable bonds with the surface (grafting onto). In the second case, polymer chains are adsorbed to the nanomaterial surface through electrostatic or dispersion interactions. Haraguchi et al. pioneered the field of nanocomposite hydrogels by utilizing exfoliated clay nanosheets in combination with a surface-adsorbing initiator. Once the polymerization was started, the clay-polymer adsorption caused gelation of the system with each clay sheet acting as a giant cross-linking point of higher functionality. Upon mechanical deformation, the reversible attachment of polymer chains together with re-orientation of clay nanosheets synergistically enabled energy dissipation. This concept was carried forth and implemented into a variety of morphologies ranging from nanospheres or nanosheets to nanofibers. To obtain tough nanocomposite hydrogels, a variety of spherical nanoparticles (NP) has been exploited based on SiO 2 , metal/metal-oxides, calcium phosphate (CaP), CaCO 3 , biochar, or rubber microspheres. Nanosheet-supported tough composite hydrogels have followed Haraguchi's example and used different forms of clay (Laponite). In addition to nanospheres and nanosheets, fibers (or fiber mats) have also been exploited to form tough (nano)composite hydrogels. To sum up, the sheer range of morphologies, dimensions, sizes combined with the various physical and chemical properties of chosen nanomaterials has made (nano)composite hydrogels a popular and successful area for the fabrication of energy-dissipating tough hydrogels.