A molecular technology that concerns changing any material from its original size and making it much, much smaller. This technology is used in a wide variety of industries, from medicine to agriculture to cosmetics. In the case of cosmetic products and over-the-counter drugs such as sunscreens, making particles nano-sized has two chief advantages: it can make the product more aesthetically pleasing (this is often the case with mineral sunscreens—making the particles of the active mineral smaller allows them to be applied without leaving a noticeable white cast), and it can enhance penetration of certain ingredients, such as vitamins and other antioxidants.

There is some concern over using nanotechnology in cosmetic products due to the risk that such small particle sizes could penetrate skin and get into the body. The United States Food & Drug Administration (FDA) is aware of the unknowns surrounding the use of nanotechnology and is researching this issue as it applies to health and human safety.

According to FDA Commissioner Margaret A. Hamburg, M.D.,  “Understanding nanotechnology remains a top priority within the agency’s regulatory science initiative and, in doing so, we will be prepared to usher science, public health, and FDA into a new, more innovative era.”

The potential issue over using nanotechnology for otherwise benign, safe cosmetic ingredients concerns the theory that by changing the ingredient size to such a degree may  result in different chemical, physical, or biological properties than the ingredients natural size. At this point there is no definitive answer on whether or not nanotechnology as it pertains to cosmetic ingredients is 100% safe. Reassuring research has emerged for certain ingredients (titanium dioxide and zinc oxide to name two) but for the time being, the FDA maintains that  "Agency experts haven’t identified specific safety concerns involving nanotechnology in FDA regulated products, but nanomaterials can, in some cases, raise safety issues. Because of this, FDA scientists continue to examine data to decide if and when additional studies are needed."