Exemplary embodiments of the invention provide a composition, in particular cosmetic, comprising a dispersion of photonic particles each having a form factor of less than 2, said particles comprising a diffracting arrangement of voids or monodisperse nanoparticles in a thermo-, electro- or photo- crosslinkable matrix. The present invention also provides a method of photo-protecting a material solar UV radiation, comprising treating said material with a composition as defined above or comprising integrating said composition into said material. More particularly, exemplary embodiments of the invention provide methods of photo-protecting materials such as paints, inks, coatings, materials manufactured from polymers, fibrous materials such as textiles, or papers, or organic or mineral glasses. Exemplary embodiments of the invention also provide a method of photo-protecting human keratinous material against solar UV radiation, a method of coloring and/or lightening human keratinous material and a method of modifying the spectral reflectance of human keratinous materials employing said composition.