Materiality is a recurring and central issue in architecture. This book explains how materials are "constructed", how they become cultural substances. Metamorphism investigates the complex relationship between natural materials and technology, science and sensuality. Gottfried Semper 1803-1879 made the notion of Stoffwechsel the key element of his theory. With this concept he intended to explain how a structural form originally bound to a method of processing is transferred from one material to another, liberated from its original function. For the first time, the book investigates the subject from a historic point of view whilst reflecting on current interdisciplinary research. Examples from Aalto to Zumthor illustrate the specific aspects of historic and contemporary material concepts.