Did you know? Stained glass was a major art form in the medieval era. It was primarily used in cathedrals and other religious structures, often with a didactic purpose of illustrating stories from the Bible or the lives of the saints for a largely illiterate populace. Cool. Thanks Bruce! They can also be a great way to add a splash of color to your MOCs. Not only do you get some historical context in this article, but you also get a lot of really nice examples.