Art Nouveau was an international style popular from 1890-1905 that emphasized organic and flowing forms inspired by nature. It influenced architecture, interior design, furniture, glasswork, ceramics, and jewelry. Key characteristics included curved lines, plant-inspired motifs, and an emphasis on harmonizing forms. Major Art Nouveau artists included Hector Guimard, whose distinctive cast iron metro entrances in Paris featured sinuous designs, and René Lalique, a renowned French jewelry designer who glorified nature in his works.