The nucleation and growth of silica colloids has been studied using real time small-angle X-ray scattering measurements. The ammonium fluorosilicate was used as precursor and both weak (NH₃) and strong base (NaOH) has been used as reducing agent for the precursor. It is observed that nucleation, growth and aggregation phenomenon occur simultaneously. The kinetics of the nucleation and growth of silica colloids depends on the strength of the reducing agent as well on its concentration. The kinetics is slow for NH₃ but is very fast for higher concentration of NaOH.