Understanding the processes by which practices become routinely embedded in everyday life is a long-standing concern of sociology and the other social sciences. It has important applied relevance in understanding and evaluating the implementation of material practices across a range of settings.This article sets out a theory of normalization processes that proposes a working model of implementation, embedding and integration in conditions marked by complexity and emergence. The theory focuses on the work of embedding and of sustaining practices within interaction chains, and helps in understanding why some processes seem to lead to a practice becoming normalized while others do not.