nucleation of phase separation

in polymer chemistry
https://doi.org/10.1351/goldbook.NT07272
initiation of phase domain formation through the presence of heterogeneities.
Note:
In a @M03872@ region of a phase diagram, @P04534@ is initiated only by nucleation.
Source:
PAC, 2004, 76, 1985. 'Definition of terms related to polymer blends, composites, and multiphase polymeric materials (IUPAC Recommendations 2004)' on page 1997 (https://doi.org/10.1351/pac200476111985)