Early written symbols were based on pictographs (pictures which resemble what they signify) and ideograms (symbols which represent ideas). Ancient Sumerian, Egyptian, and Chinese civilizations began to adapt such symbols to represent concepts, developing them into logographic writing systems. Pictographs are still in use as the main medium of written communication in some non-literate cultures in Africa, the Americas, and Oceania. Pictographs are often used as simple, pictorial, representational symbols by most contemporary cultures. Pictographs can be considered an art form, or can be considered a written language and are designated as such in Pre-Columbian art, Native American art, Ancient Mesopotamia and Painting in the Americas before Colonization.