Every morning, many Americans start their day with a bowl of cereal. Some spend time while they eat breakfast reading the back of the cereal box, but few consider its size, shape, and construction, or realize that it was designed by an engineer. This article describes a lesson in which students design, build, and critique cereal boxes. The lesson follows the 5E learning-cycle model and incorporates engineering and measurement, with a focus on mathematics and the relationship between surface area and volume.