In the II-III transition, however, we observed a slight expansion to the crystal without thermosalient behavior (Figure ). The change did not conform to the unit cell changes, as polymorph III exhibits a vastly different symmetry and unit cell relative to polymorph II (Figure ) and results from thermal expansion during heating. This reconstructive transition also leads to the formation of multiple grain boundaries within the crystal, breaking single crystallinity (Figure ). Formation of these domains mitigate strain build up preventing any thermosalient motion from occurring due to the crystal expansion. These observations are consistent with the understanding that the nucleation and growth mechanism does not incur shape change owing to a single-to-polycrystalline transition . This stands in contrast to the cooperative martensitic transition that preserves single crystallinity and thus exhibits shape reversibility corresponding to the unit cell change.