Stained glass windows, emblems of Art nouveau

Stained glass was used as part of architectural research, which was particularly abundant in Nancy at the beginning of the 20th century.

As a barrier between the outside and the inside, stained glass absorbs the sun's rays and reflects some of them back, producing a light that is no longer neutral but coloured, and giving interiors an atmosphere often referred to as "aquarium". It is interesting to note that stained glass adapts to architectural styles that sometimes require complete opacity. It may be required to mask a mediocre environment as in Gruber's La Salle gallery. Or to give the illusion of a garden, as in the Les Roses stained glass window designed for the Corbins' flat (rue Mazagran, Nancy). On the other hand, the windows of verandas, bow windows and windows overlooking the garden were fitted with non-opaque stained glass,  allowing the viewer to enjoy the natural surroundings. Examples include Gruber's Pomme de Pin stained glass window in the eponymous salon on the ground floor of the museum, and Ventrillon's 1923 window depicting a basket of flowers for the French window in the 1920s wing of the Corbin house.

Technical innovations contributed to the decorative effect, like the superimposition of layers of glass, acid etching, chenille glass and American glass (invented by Tiffany), combined with grisaille painting. Although the iconography was essentially inspired by plants, the human figure was also present, notably in Henri Bergé's La lecture. Stained glass could also be used for advertising purposes, as in the case of Canard-Duchêne champagne, with a stained glass window made by Joseph Janin.

The musée de l'École de Nancy houses around 150 stained glass windows dating from the end of the 19th century to the eve of the Second World War: ranging from Art nouveau to Art Deco.