Conversion, adaptation, reuse - these techniques are as old as construction itself. However, since the industrialization of the building industry and the emergence of modernism in architecture, newly constructed buildings have dominated our idea of good and progressive architecture. For decades, conversion did not play a significant role in architectural practice.Today, things have changed. The industrialization of the construction industry has led to environmental degradation, and the reform potential of modernism has been exhausted. Consequently, the existing building stock is one of the resources - perhaps even the most important resource - for the transformation of our cities. Against this backdrop, the architecture of conversion has made an unexpected comeback. Young architects in particular are providing surprising answers to the environmental and social questions of our time with their conversion projects.This book introduces 30 examples that illustrate how seemingly everyday conversions can be turned into groundbreaking architecture, while eight essays shed light on the important role of conversion in history and the theory of architecture.