The introduction of Pointillism was a personal response by the French artist Georges Seurat to the issues of light, form, and colour that had preoccupied the Impressionists up to that time. Starting in 1886, he developed a technique of painting with dots that was based on the scientific classification of colours by the physicist Chevreul. Unadulterated dots of colour are systematically placed alongside each other so that the optical blending takes place in the eye of the beholder when one observes from some distance. The result is a vivid, vibrating spectacle of reverberations of light and a refined representation of varying atmospheric perceptions. This painting innovation soon made an international impact, in part thanks to the presence of Seurat and Signac at the salons of Les XX and La Libre Esthétique. In Belgium the young Henry Van de Velde emerged as the movement’s most important representative.