This introduction presents an overview of key concepts covered in the subsequents chapter of this book. The book is based on a simple but often forgotten premise: that what actually happens in practice is significantly different from what is theoretically supposed to happen. It also contributes to the field of migration studies and the public debate on immigration in Europe, but through on a detour from the more traditional approaches to the field. The book examines the process of applying immigration law to individual cases through an investigation into the practice of decision-making and migration management in German immigration offices. It considers the effects of the chaotic, uneven and varying implementation practices. The book links variations and explanatory domains back to the original research question and its theoretical foundation. In the rather strange sense, the German administrative system is no less exotic than the 'pre-modern' tribes of classic anthropology.