A surprising trick that allows a beam of light to be completely absorbed even in the thinnest of layers: Using mirrors and lenses, a 'light trap' can be constructed, in which the light beam is steered in a circle and then superimposed on itself -- exactly in such a way that the beam of light blocks itself and can no longer leave the system. Thus, the light has no choice but to be absorbed by the thin layer -- there is no other way out.