In this activity, learners discover that nanoparticles of gold can appear red, orange or even blue. They learn that a material can act differently when it’s nanometer-sized. Use this activity to explain how stained glass gets its different colors. Note: the cost for the materials in this activity is quite high. However, this is a one-time cost, since the nano gold is kept in vials at all time and thus should not be used up. SAFETY: Do not let visitors ingest the contents of the vials. Keep vials sealed shut. Use caution when handling the stained glass samples. Do not remove them from their protective case.