Water in oil(w/o) microemulsion had been used to prepare magnetic iron oxides nanoparticles with different microemulsion number density of Fe2+ and OH-. The as-synthesized magnetic iron oxides nanoparticles had been characterized by XRD, TEM, BET and AGM. The XRD result showed that the crystallite size of the samples was in the range of 3-8nm in diameter whereas the mean particle size obtained from TEM was in the range 2-6nm. For the least upper bound magnetic, size of these particles was at the range of 1-7nm. Due to the agglomeration, BET showed different result. The trend of the particles...