The size distribution and swelling kinetics of copolymer nano-spheres extracted from an W/O emulsion was studied with dynamic light scattering (DLS) and transmission electron microscopy (TEM). TEM results were compared against DLS results. It was demonstrated that the size distribution for agglomerates (clusters) of particles match well with the size distribution obtained from DLS. Hence, less time consuming DLS tests can be used for the estimation of the size of nano-spheres in the future. Next, a novel procedure for the study of agglomeration and swelling rates separately with TEM was designed. The results of the study revealed that the spheres agglomerate and swell over time. The kinetics of the agllomeration is used for a population balance model to predict the size of spheres over time. This approach helps to understand how well the spheres can propagate in an oil reservoir over time.@en