Art Nouveau is an elegant decorative art style characterized by flowing lines and natural organic forms, often intricately detailed. Somewhat rooted in the British Arts and Crafts Movement of William Morris, Art Nouveau became popular across Europe and in the United States. Leading practitioners included Aubrey Beardsley, Gustav Klimt, Alfons Mucha, and the American glassmaker Louis Comfort Tiffany. Art Nouveau remained popular until about the time of World War I, and was ultimately replaced by the Art Deco style.