Nanoparticles are insoluble or bio-persistent materials ranging in size from 1 to 100 nm. In cosmetics, the nanoparticles permitted in the annexes of the European Regulation are carbon black as a colourant, and titanium dioxide, zinc oxide, the tris-biphenyltriazine, the methylene bis-benzotriazolyltetramethylbutylphenol (MBBT) as ultraviolet filters. These elements are currently the subject of controversy due to their potential toxicity to health and the environment. Focus.