Edgar Degas's influence upon Mary Cassatt has long been acknowledged, but her role in shaping his artistic production and in preparing the way for his warm reception in America is fully examined for the first time. These two major figures of the impressionist movement shared a keen observer's eye, as well as openness to experimentation. Despite differences of gender and nationality, they built a deep friendship based on mutual respect and admiration for each other's talents. Focusing on the critical period from the late 1870s through the mid-1880s, when Degas and Cassatt were most closely allied, this book brings together some seventy works in a variety of media to examine the fascinating artistic dialogue that developed between these two celebrated artists. Technical analysis provides new insight into the intersections between their art in terms of choice of media and methods as well as subject matter. The authors also examine the artists' participation in the unrealised collaborative impressionist publication Le Jour et la Nuit, which resulted in some of their most exceptional prints. Another focus is a series of prints, pastels, and paintings produced by Degas on the theme of Mary Cassatt at the Louvre. A number of works exchanged between the two artists serve as a tangible testament to the affinity between Degas and Cassatt and show both artists as collectors and champions of each other's art.