The study was done to demonstrate that nanoparticles are more toxic than fine particles, even if they have the same chemical composition. The toxicity of a particle within a single cellular system is dependent on several properties including shape, size, chemical composition, and surface charge along with the intrinsic biological pathways activated in a cell following their uptake. The higher toxicity by nanoparticles compared to fine particles having the same chemical composition is due to the higher density of surface molecules presenting them with a higher surface charge and a larger surface area to react. A Fe(III) nanoparticle behaves like a catalyst providing the space and the proper environment for the biomolecules to react with oxidizing elements. Due to the special properties nanoparticles retain. Their utilization will increase leading to the advancement of nanotechnology in almost every industrial sector. In view of the potential toxic effects of these particles it must be recommended, that special care should be taken during their production to minimize the exposure of workers. Special emphasis should be laid on the charge and intracellular retention properties when nanoparticles are used for medical purposes such as thermal imaging and cancer drug targeting. This recommendation should be specially implemented for the poorly soluble nanoparticles made out of inorganic compounds such as the iron-containing nanoparticles.