The Greedy Triangle, by Marilyn Burns, has served to introduce students to several new shapes.  In the story, the unhappy triangle is dissatisfied with his life has a three-sided shape.  Again and again he visits the shapeshifter to gain more sides, turning into a quadrilateral, pentagon, hexagon, heptagon, octagon, nonagon, and decagon.  However, in the end, the triangle decides his life was better as a triangle and he returns to his original shape.  As the triangle was transformed, students were exposed to new vocabulary and real life examples of many of these shapes.  We are further exploring each of these beginning with quadrilaterals.  Students have created quadrilaterals using geo-boards, identified quadrilaterals in the classroom, and are learning about properties of quadrilaterals in designing and completing individual booklets.