The process of crystallization begins with the nucleation of a small crystal (or seed), which successively grows into microcrystalline domains at the expense of surrounding amorphous ones. While this process has been observed for (semi-)crystalline, bulk polymers or strain-crystallizing rubbers, it can also occur in hydrogels, as seen in those based on poly(vinyl alcohol) (PVA). On a molecular level, the PVA chains arrange into a well-defined lattice structure (supported by hydrogen bonding) and are surrounded by an amorphous incompatible bulk phase that lacks any long-range order. The crystalline regions can then act as physical cross-links due to their increased rigidity, higher local mechanical stiffness, and the reversible packing. PVA is a prime example where such microcrystallites can be triggered via temperature to mediate gelation and has seen avid interest for the fabrication of tough hydrogels. Another type of microphase separation can occur through the salting-out effect, which was originally observed in protein chemistry. When weakly polar solutes are dissolved in water, certain salts can deprive the solute from its hydration shell, reduce solute-solvent interactions and solute solubility, which eventually leads to its precipitation. The saltingout effect is more pronounced by anions and follows the socalled Hofmeister series: