Petrification is a process, but it also can be understood as a concept. This volume takes the first steps to manifest, materialize or “petrify� the concept of “petrification� and turn it into a tool for analyzing material and social processes. The wide array of approaches to petrification as a process assembled here is more of a collection of possibilities than an attempt to establish a firm, law-generating theory. Divided into three parts, this volume twenty-plus authors explore petrification both as a theoretical concept and as a contextualized material and social process across geological, prehistoric and historic periods.  Topics connecting the various papers are properties of materials, preferences and choices of actors, the temporality of matter, being and becoming, the relationality between actors, matter, things and space (landscape, urban space, built space), and perceptions of the following generations dealing with the petrified matter, practices, and socialrelations. Contributors to this volume study specifically whether particular processes of petrification are confined to the material world or can be seen as mirroring, following, triggering, or contradicting changes in social life and general world views. Each of the authors explores – for a period or a specific feature – practices and changes that led to increased conformity and regularity. Some authors additionally focus on the methods and scrutinize them and their applications for their potential to create objects of investigation: things, people, periods, in order to raise awareness for these or to shape or “invent� categories. This volume is of interest to archaeologists, geologists, architectural historians, conservationists, and historians.