In this lesson, students learn that scientists and engineers are catalysts. They read about Isatou Cessay in the book One Plastic Bag: Isatou Ceesay and the Recycling Women of the Gambia, by Miranda Paul. After reading, students test different types of plastics for strength and create a new design just as Isatou Ceesay did with the families of her community. This book selection highlights the practice of constructing explanations and designing solutions, and it includes the Table of Contents, Foreword, Acknowledgments, About the Authors, and Index.