Sculpture is three-dimensional artwork created by shaping or combining hard materials typically stone such as marble or metal, glass, or wood. Softer (“plastic”) materials can also be used, such as clay, textiles, plastics, polymers and softer metals. Carving stone into sculpture is an activity older than civilization itself. Prehistoric sculptures were usually human forms. The process begins with the selection of a stone for carving. Some artists use the stone itself as inspiration; Michelangelo claimed that his job was to free the human form trapped inside the block.