The way in which sunscreen products work is usually explained in terms of absorption and scattering of UV radiation by sunscreen filters. Soluble filters absorb UV radiation and emit it again as lower-energy, longer-wave heat radiation. The insoluble or particulate filters scatter UV radiation, while nanoparticulate filters primarily absorb UV-radiation. However, this information is not very helpful when it comes to imagining what happens to a sunscreen product when it is applied onto the skin and what actually happens on the spot of application. The following explains what happens ON and IN the skin.