Georges Seurat (1859-1891) : Depending on your point of view, either an impressionist or a neoimpressionist. Painted in the pointillist style, he took a rarely-used technique and showed what could be done with it. His paintings were often luminous, with big, solid shapes in them. The pointillism is important, but don't fail to notice his mastery of composition; it's hard to move any one object out of place without breaking the painting.