Direct observation of transient Ostwald crystallization ordering from racemic serine solutions.

The Ostwald rule of stages describes the conjectured transitioning through metastable polymorphic crystal structures during crystallization. Direct observation of the Ostwald rule of stages using was performed using solutions of simple amino acids by second-order nonlinear optical imaging of chiral crystals (SONICC). SONICC, which is based on second-harmonic generation (SHG) imaging, enabled detection of homochiral microcrystals that survived only a few seconds before being converted to the more stable SHG-inactive polymorphic forms.