Seurat's most significant contribution to art was the development of pointillism, a technique where small, distinct dots of pure color are applied in patterns to form an image. This method, also known as divisionism, was based on the scientific theory of optical mixing, where the viewer's eye blends the dots into a cohesive image.

Seurat's magnum opus, "A Sunday Afternoon on the Island of La Grande Jatte" (1884-1886), epitomizes his pointillist technique. This monumental canvas, depicting Parisians at leisure, took two years to complete and comprises millions of meticulously placed dots. The painting's success catapulted Seurat to fame and solidified pointillism as a legitimate artistic movement.