Infants entering the early years of childhood become increasingly active and curious about the world around them. Toddlers delight in toys that surprise them with motion and noise, toys that encourage them to develop their motor skills. Children take pull and push toys with them, for instance, as they journey around the playroom, and the toys often reward their efforts with a mechanical reaction, the movement of a rider on his horse or the chiming of a bell, for instance. Early examples of pull and push toys date back several centuries, and by the 19th century they appeared in many forms, made of tinplate, cast iron, or wood, and often enhanced with mechanical components or brightly lithographed decorations. Push and pull toys remain in production in the 21st century.