This is a close up of the Favrile glass tiles in the ceiling of the old Marshall Fields department store, now Macy's, on State Street in Chicago. The store opened in September 1907, and included a Tiffany Ceiling that is both the first and largest ceiling ever built in favrile glass, containing over 1.6 million pieces. Favrile glass is a type of iridescent art glass designed by Louis Comfort Tiffany. The color is ingrained in the glass itself with distinctive coloring. Favrile glass was used in Tiffany's stained-glass windows. Here's another picture showing the whole ceiling six stories up. Canon G11, 1/20 sec @ f/6.3, ISO 400.