Artistic medium, generally found in the form of windows or autonomous panels composed of coloured glass. It is the only such medium to be observed through refracted and not reflected light. The variety and quality of light passing through the translucent panels depends on the time of day and season; it is also affected by the texture of the glass. The highest achievements in the art of stained glass were those of the Gothic era in Europe and those of the Gothic Revival during the 19th century.