On of the various materials used and creative methods involved in artistic production, media being the plural form (though this latter term is often used more specifically of the various forms in which news is conveyed). In the visual arts, the artist must use some physical means or medium to realize an idea, though the conceptual art of the latter half of the twentieth century came to challenge even this idea. In painting, medium may refer to the the liquid that carries the pigments, for example, linseed oil for oil paints, or egg yolk for egg tempera; this is sometimes also called the base or vehicle. Longstanding sculptural media include marble, terra cotta and bronze, for example. Mixed media works use a combination of materials typically or traditionally developed separately.