Gold and silver nanoparticles
Plasmonic nanoparticles (Au and Ag) have been object of fascination since ancient time for the preparation of stained glass. Such elementary building block are extremly robust and their use in monuments stand the test of time. A not too far example from the laboratory is the "Sainte-Chapelle du Palais" at "l'île de la cité" in Paris (see image, wikipédia). This phenomenon, commonly witnessed by everyone, originates from the electromagnetic properties of metallic nanoparticles.