Young children love to build. They can learn a lot about structure and design by building with many different kinds of materials. A package of paper or plastic cups, a bunch of old cardboard boxes, or a collection of paper towel rolls make interesting and very unique building materials for children to experiment with. What material works best for making a bridge for toy cars? What works best for making a tall tower? What is it about the item's material, shape, or size that makes it work so well for the job?