This play set requires Play-Doh, the soft, molding compound used by kids everywhere since the middle of the 20th century. Play-Doh originated as a variant of a cleaning compound used to improve the look of soot-stained wallpaper in homes heated by burning coal. Joe Vickers of Kutol Chemicals in Cincinnati sent the cleaning material to his sister-in-law, a teacher who had complained that her nursery-school children could not manipulate the modeling clay supplied by her school. At first, Vickers sold Play-Doh in gallon cans, thinking that his primary market would be school systems. By 1956, however, Rainbow Crafts, a new company name to reflect the variety of Play-Doh colors available, sold the modeling compound in three-pack sets of red, blue, and yellow seven-ounce cans. Placing the compound in major department stores boosted sales, but the product really took off when it was featured on the popular children's show "Captain Kangaroo." Play-Doh remains a very popular toy more than fifty years later. Most Americans recognize its distinctive almond aroma and recall hours of modeling, molding, and manipulating the compound. Since the introduction of Play-Doh as a staple of the playroom, two billion cans have been sold--enough to roll out a multi-colored snake of the substance that would circle the earth three hundred times.