Spinodial decomposition

However, microsyneresis may also be caused or facilitated by inhomogeneities already present in the network (such as those in Fig. 12). The microsyneresis can then be relatively stable and its occurrence reversible. In many cases microsyneresis need not be a fully reversible process and may be accompanied by strong hysteresis effects — compare supercooling or superheating — or the formation of the new phase may take place only when the limit of the absolutely unstable region is surpassed (spinodial decomposition mechanism (25)). 

Cahn, J. W. Phase separation by spinodial decomposition in isotropic systems. J. Chem. Phys. 42, 93 (1965). 

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