A paradigmatic example of non-classical nucleation worth mentioning is the prenucleation cluster pathway. The prenucleation cluster (PNC) pathway was first proposed for CaCO 3 but has since been attributed to phase separation in a diverse range of systems. The PNC pathway suggests that the parent solution phase is comprised of hydrated solute clusters in pseudo-equilibrium with solvated monomers. The population of PNC sizes is determined by the equilibrium constant (𝐾) for the reaction (monomer)𝑥 +monomer