The term Post-Impressionism, which arose from a famous exhibition held in London in 1910, is, like most other "isms" in art, a nebulous one. In its broadest sense it can be used to describe the work of a number of painters who, often working independently from one another, evolved a style that originated, in part, from their reaction against the Impressionists. Although several of these artists began their careers exhibiting with the Impressionists, they soon developed a style of painting that was much more concerned with structure and form. Less interested in the transitory effects of light and motion than the Impressionists, they often turned instead to different subjects, which they painted with a greater emphasis on formal discipline. In a sense, these heirs of the Impressionists were returning, knowingly or unknowingly, to some of the traditional principles of painting that were so brilliantly exemplified by David and Ingres in the first half of the nineteenth century.