The Greedy Triangle by Marilyn Burns is a great book to introduce young children to polygons. In the book, the unhappy triangle wants to change into a new shape and so the adventure through the polygons begins! I created 3 activities to accompany the book: a sorting activity with 28 given shapes included, an art activity and an inquiry lesson comparing a polygon to a non-polygon shape. In addition, Marilyn Burns has some great extension activities listed in the back of the book. This is a great cross-curricular activity for the Math classroom.