Teachers can introduce slicing and the mathematics of cross sections in many ways, but the most direct is simply to have students physically slice real objects into cross sections. We suggest lining tables with large sheets of paper or disposable tablecloths for easier cleanup. Denser and drier objects seem to work better; apples, zucchini, bagels, sponge cake, Play-Doh, cheese, and pineapple all work well. Students can use either sharp knives or thin wire to cut the cross sections (see fig. 2).