These drinking glasses are made for a night use. Photoluminescent pigments are included between two layers of glass during the hot glass making process. The glass or the rock is designed to be exposed under one natural or artificial of strong intensity during ten minutes to reload the photolominescent pigments and then take advantage several hours of the glow-in-the-dark effect. Just like in the fairy tale of 'Le petit poucet' ( the tale of a little boy who finds back his way home after having put rocks on his way to remember it), we have now the possibility to find our path in the dark thanks to the night rocks.