The in situ, real-time, photon transmission technique was used to monitor the free-radical crosslinking copolymerization (FCC) of acrylamide (AAm) and N,N'-methylenebisacrylamide (Bis). Gelation experiments were performed with various Bis contents at various wavelengths. It was observed that the transmitted photon intensity, I-sc, decreased dramatically at a certain reaction time, which is attributed to the increase in scattered light intensity, I-sc, during the formation of microgels in the system. The increase in I-sc was modeled using Rayleigh's equation where the reaction time was found to be proportional to the volume of the microgels. In most cases, the change in I-sc was found to be inversely proportional to the 2.5 power of the wavelength, lambda, from which the size of the microgel particles were estimated during the FCC.