What do we call the colored glass windows in many cathedrals?

The story behind the answer

Medieval artisans colored molten silica with metallic oxides—cobalt for deep blues, copper and gold for reds—then cut the glass into pieces and joined them with lead cames. Artists fired on enamel paints for details, but the color lives within the glass, not merely on its surface. That’s why it isn’t just “painted” or “tinted,” and “leaded” refers to the framework, not the art itself.

From the 12th-century Gothic era, builders like Abbot Suger championed lux nova—“new light”—filling churches with narrative windows that taught Bible stories to largely illiterate congregations. Masterworks such as Chartres’ rose windows and its famed deep blue transformed heavy stone walls into luminous storytelling panels.