In this challenge you will create a model of a "rock stack" using playdoh. You can also use toothpicks and paper clips if you think they might be helpful, but that is it! You must make spheres of different sizes using the modeling clay and stack them in one vertical stack. It must stand on its own for 1 minute or more. To count, your stack must be at least 5 inches tall, but the number of spheres will determine the winner. The current record is 15!