Nanomaterials are materials with individual parts or dimensions on the nanoscale, about one billionth of a metre - the scale of atoms and molecules. The properties of nanomaterials differ from the bulk forms of the same material: they might be stronger, lighter, or more reactive and they can be used in different ways than in their larger form. For instance, gold in its bulk form is very stable and non-reactive and that is why it can be stored safely for centuries. Nano-gold reactivity, however, is quite different - it can be used as a catalyst to facilitate chemical reactions. These new properties have the potential for great impacts in electronics, medicine, and other fields. However, while engineered nanomaterials can provide great benefits, we know very little about their potential effects on human health and the environment.

Nanotechnologies make use of very small objects. Nanomaterials are an increasingly important product of nanotechnology. They contain nanoparticles, smaller than 100 nanometers in at least one dimension. Nanomaterials are coming into use in healthcare, electronics, cosmetics and other areas. Their physical and chemical properties often differ from those of bulk materials, so they call for specialized risk assessment. This needs to cover health risks to workers and consumers, and potential risks to the environment.

Nanoparticles are defined as particles dispersions or solid particles with a size in the range of 10-1000nm. Nanoparticles as a drug delivery system are to control particle size and release of pharmacologically active agent in order to achieve the site-specific action of the drug at the therapeutically optimal rate.

Nano powders have wide range of applications and different methods are available for production. In the paper the three methods discussed are mainly used in pharmaceutical industries and electronic industries for the production of nano powder. If we compare the two processes (PGSS) and (DELOS) Process there is difference between the shapes of the powder in (PGSS) Powder is spherical and in (DELOS) there are cylindrical and dendrite. The powder produced in (PGSS) is in amorphous form where has in (DELOS) it is crystalline form. In the above methods (PGSS) process is more advantageous than any other process because it is flexible as we can control the size of the powder produced by controlling the amount of super critical fluid used in the process and we can maximize and minimize the yield of the production.

In recent years, much attention has been paid to the synthesis and study of nanoparticles because of wide range of potential applications. Particularly, magnetic nanoparticles can have the special characteristic of exhibiting single-domain magnetism and can be used in magnetic tapes, ferrofluid, magnetic refrigerants, etc, because of their ultra fine size dimensioned with magnetic domain size. Oxide coated iron nanoparticles are non-toxic materials and due to enhanced magnetic properties can be more effective as compare with magnetite nanoparticles for biomedical application.