The lecture surveys the history, material, technique, and spiritual role of stained glass, tracing its relationship with mosaic and fresco and noting a medieval high period followed by later domestic adaptations. It explains how coloured glass is produced by adding metallic oxides, describes flash glass and surface-etching techniques, and outlines painting, cutting, and assembly practices that have remained largely continuous. Emphasis is placed on stained glass as a means of modifying light and deepening religious mood, on the use of symbolism and typology in imagery, and on recent revivals and innovations introduced by artists trained at the art college.