The term stained glass refers either to the material of colored glass or to the art and craft of working with it. Throughout its thousand-year history the term "stained glass" was applied almost exclusively to the windows of churches, cathedrals and other significant buildings. Although traditionally made in flat panels and used as windows, the creations of modern stained glass artists also include three-dimensional structures and sculpture.
Stained glass, as an art and a craft, requires the artistic skill to conceive an appropriate workable design, and the engineering skills necessary to assemble the decorative piece, traditionally a window, so that it will fit snugly into the window frame for which it is made and also, especially in the larger windows, is capable of supporting its own weight and surviving the elements. Many large windows have withstood the test of time and remained substantially intact since the late Middle Ages. In Western Europe they constitute the major form of pictorial art to have survived. In this context, the purpose of a stained glass window is not to allow those within a building to see the world outside or even primarily to admit light but rather to control it. For this reason stained glass windows have been described as 'illuminated wall decorations'.
The design of a window may be non-figurative or figurative. It may incorporate narratives drawn from the Bible, history or literature, or represent saints or patrons. It may have symbolic motifs, in particular armorial. Windows within a building may be thematic, for example: within a church - episodes from the life of Christ; within a parliament building - shields of the constituencies; within a college hall - figures representing the arts and sciences; or within a home - flora, fauna or landscape.
