The period saw intense experimentation with the medium of the book and its components of page, illustrations, and text. Dialogues between artists and writers—such as collaborations between the poet Guillaume Apollinaire and the artist Raoul Dufy, or between the poet Blaise Cendrars and the artists Sonia Delaunay and Fernand Léger—resulted in innovative interpretations of the illustrated book. Cendrars’s poem La Prose du transsibérien et de la petite Jehanne de France, illustrated by Delaunay, was called the first simultaneous book, meant to engage text and image, colors and words, on the same level and at the same time.