stylistic:tone
Characteristics, decoration and motifs

Early Art Nouveau, particularly in Belgium and France, was characterized by undulating, curving forms inspired by lilies, vines, flower stems and other natural forms, used in particular in the interiors of Victor Horta and the decoration of Louis Majorelle and Émile Gallé. It also drew upon patterns based on butterflies and dragonflies, borrowed from Japanese art, which were popular in Europe at the time.

Early Art Nouveau also often featured more stylised forms expressing movement, such as the coup de fouet or " whiplash " line, depicted in the cyclamen plants drawn by designer Hermann Obrist in 1894. A description published in Pan magazine of Hermann Obrist 's wall hanging Cyclamen (1894), compared it to the "sudden violent curves generated by the crack of a whip," The term "whiplash", though it was originally used to ridicule the style, is frequently applied to the characteristic curves employed by Art Nouveau artists. Such decorative undulating and flowing lines in a syncopated rhythm and asymmetrical shape, are often found in the architecture, painting, sculpture, and other forms of Art Nouveau design.

Other floral forms were popular, inspired by lilies, wisteria and other flowers, particularly in the lamps of Louis Comfort Tiffany and the glass objects made by the artists of the School of Nancy and Émile Gallé. Other curving and undulating forms borrowed from nature included butterflies, peacocks, swans, and water lilies. Many designs depicted women's hair intertwined with stems of lilies, irises and other flowers. Stylised floral forms were particularly used by Victor Horta in carpets, balustrades, windows, and furniture. They were also used extensively by Hector Guimard for balustrades, and, most famously, for the lamps and railings at the entrances of the Paris Metro. Guimard explained: "That which must be avoided in everything that is continuous is the parallel and symmetry. Nature is the greatest builder and nature makes nothing that is parallel and nothing that is symmetrical."

Earlier Art Nouveau furniture, such as that made by Louis Majorelle and Henry van de Velde, was characterized by the use of exotic and expensive materials, including mahogany with inlays of precious woods and trim, and curving forms without right angles. It gave a sensation of lightness.

In the second phase of Art Nouveau, following 1900, the decoration became purer and the lines were more stylised. The curving lines and forms evolved into polygons and then into cubes and other geometric forms. These geometric forms were used with particular effect in the architecture and furniture of Joseph Maria Olbrich, Otto Wagner, Koloman Moser and Josef Hoffmann, especially the Stoclet Palace in Brussels, which announced the arrival of Art Deco and modernism.

Another characteristic of Art Nouveau architecture was the use of light, by opening up of interior spaces, by the removal of walls, and the extensive use of skylights to bring a maximum amount of light into the interior. Victor Horta 's residence-studio and other houses built by him had extensive skylights, supported on curving iron frames. In the Hotel Tassel he removed the traditional walls around the stairway, so that the stairs became a central element of the interior design.