Objects made of glass – in particular the clear “crystal glass” – fascinated early modern people. In addition, the optical effects were particularly admired. A polished glass object had the effect of a prism that let the light shimmer in the colours of the rainbow. But the possibility of storing odd things inside glass vessels was also part of the fascination. Behind glass they were clearly visible, but could not be touched. These objects included relics kept in glass vessels or three-dimensional miniatures shown inside bottles (impossible bottles).