two-stage varying-temperature technique was utilized to study the nucleation/crystallization kinetics of nanosized faujasite zeolites from clear solutions. At 100 C, the nucleation period of zeolite Y was determined to be about 6.5 days, which extended over almost the whole period of crystal growth. The crystallization kinetics of colloidal zeolite Y differed from those for another clear solution, colloidal zeolite system, namely, TPA-silicalite-1, where the nucleation and crystal growth were found to occur as separate processes. Despite the occurrence of simultaneous nucleation and crystal growth, the colloidal zeolite Y product had a crystal size distribution similar to that for TPA-silicalite-1. In addition, the influence of the growth-limiting nutrient (Na+) on the crystallization of zeolite Y was investigated. The sodium concentration in the synthesis solution could be controlled below a critical level to avoid the nucleation of zeolite A.