Supersaturation is the driving force of the crystallization, hence the rate of nucleation and growth is driven by the existing supersaturation in the solution. Nucleation and growth continue to occur simultaneously while the supersaturation exists. The crystal growth is the subsequent growth of the nuclei that succeed in achieving the critical cluster size. It is at the stage of nucleation that the atoms arrange in a defined and periodic manner that defines the crystal structure - note that 'crystal structure' is a special term that refers to the relative arrangement of the atoms, not the macroscopic properties of the crystal (size and shape), although those are a result of the internal crystal structure. Such critical size is dictated by the operating conditions ( temperature, supersaturation, etc.). Therefore, the clusters need to reach a critical size in order to become stable nuclei. However, when the clusters are not stable, they redissolve. These stable clusters constitute the nuclei. Nucleation is the step where the solute molecules dispersed in the solvent start to gather into clusters, on the nanometer scale (elevating solute concentration in a small region), that become stable under the current operating conditions. The crystallization process consists of two major events, nucleation and crystal growth. See also crystallization dynamics section. The video covers an area of 2.0 by 1.5В mm and was captured over 7.2 min.

Time-lapse of growth of a citric acid crystal. Process File:CitricAcid Crystalisation Timelapse.ogg

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