To elaborate further on these preliminary stages, La Mer introduced the first approach to a nucleation system in colloidal suspensions . According to La Mer, the process occurs in three stages: (i) pre-nucleation, (ii) nucleation, and (iii) crystal growth , as shown in Figure (a). Pre-nucleation usually occurs because of the absence of precipitates in an unsaturated solution. However, the application of precipitating agents leads to an increase in the concentration of the precursor species.