The theme of Scale and Structure (or simply Scale) appears in many state science frameworks and projects of national importance. The major idea of this theme is that a change in scale will affect the nature of the given structure. This book is designed as a guide and set of activities for third- through eighth-grade teachers. The activities included are designed to help students develop a feeling for and an understanding of structure and how it changes with scale change. This book should be considered as a collection of starting points that provide endless opportunities for sustained investigations and experimentation. The activities explore a set of phenomena using different materials and approaches, thus allowing students to develop a better understanding of the phenomena over time. The book is divided into four sections: teaching scale and structure, the physics and engineering of structure, the mathematics of scale, and the effect of scale on structure. Appendices include a resource guide, blank charts for mathematics of scale activities, and sample science record sheets. (JRH)