Tristan Tzara, often credited as the founder of the Dada movement, met Robert and Sonia Delaunay when they moved back to Paris in 1921. The couple, who were at the center of the avant-garde artistic scene, became close friends with Tzara, beginning a prolific artistic relationship. Sonia Delaunay and Tzara collaborated on her "dress poems," which featured texts by Tzara woven throughout Delaunay's colorful, geometric and ecstatic garments. She designed costumes for his absurdist play Le Cœur à gaz (The Gas Heart) in 1923 and illustrated many of his published collections of poems, including Le fruit permis from 1956, thirty-five years after they had initially met.