1. Context

Many everyday products contain nanoparticles. The addition of silica oxide makes table salt more fluid, carbon black increases the wear resistance of tires, and the use of different particle ranges enhances the optical properties of make-up. The range of products containing fine to very fine particles is vast: ultraviolet (UV) filters contained in sun protection products, self-cleaning surfaces (lotus flower effect), specific functional surfaces with, for example, greater bioavailability of pharmaceutical agents, higher catalytic activity or greater chemical reactivity, scratch-resistant surfaces due to increased material hardness, etc. (see table 1 ). More than a thousand companies worldwide are contributing to the development and establishment of particles with new or improved properties.