In the space of only a few years the scientists Odgen Rood, Michel-Eugène Chevreul and Charles Henry each published theories of light and color in which they analyzed the differentiation between color-light and color-pigment and suggested a connection between musical theory and emotive line. Their findings provoked the interest of a group of young artists who were frustrated by the Impressionists' approach to painting the effects of light and atmosphere. These artists began to experiment with the scientific notion of optical mixing by creating forms out of small dots of pure pigment in their painting. Though Cross was friendly with many of the painters who comprised what came to be called the Neo-Impressionist group, he did not start painting divisionist pictures until after Georges Seurat's death in 1891 and, when he did, he quickly developed his own variant of their technique. He abandoned their use of the dot in favor of separated rectangular strokes of pure pigment that he applied in a manner not unlike the tessera in mosaics. Cross constructed his compositions with interlocking planes and careful juxtaposition of complementary colors. A letter from Cross to Paul Signac dated 1 September 1895 explained that his ultimate aim was to have "technique cede its place to sensation" (I. Compin, op. cit., Paris, 1964, p. 42).
Cross's chronic rheumatism required that he move to a warmer climate and in 1891 he chose to settle in the village of Saint-Clair, close to his friend Paul Signac's home in Saint-Tropez. There he worked outdoors, producing small drawings and watercolors that he later developed into finished paintings in his studio. The Mediterranean topography of the Côte d'Azur provided him with the inspiration to use a brighter palette and flatter forms. La sieste au bord de la mer exemplifies Cross' ability to convey the effects of the vibration of color and the rhythm of form. With its palette of brilliant yellows, vivid reds, lush greens and indigo blues, it presages the work of the Fauves who were drawn to this same coast just a few years later. Maurice Denis remarked, "The sun is not for him a phenomenon which makes everything white, but is a source of harmony which hots up nature's colors, authorizes the most heightened color-scale, and provides the subject for all sorts of color fantasies" (quoted in J. House, Post Impressionism, exh. cat., The Royal Academy of Art, London, 1979, p. 61). The inclusion of bathers was also a frequent feature of Cross' Midi paintings, and in the present picture he depicts a group of women discreetly assembled in an idyllic cove. In a letter to Theo van Rysselberghe Cross wrote, "On the rocks, on the sand of the beaches, nymphs and Naïads appear to me, a whole world born of beautiful light" (quoted in Neo-Impressionism, exh. cat., The Solomon R. Guggenheim Museum, New York, 1968, p. 47).