This chapter provides a detailed overview of contemporary sociomaterial and practice-based approaches, focusing in particular on their implications for conceiving workplace learning. It lays the theoretical foundations for the analysis and arguments developed in Parts II and III. It sets out an ontological position, and key concepts that are not so much applied in the subsequent empirical work, but tangled up in it (including in the approach to ethnographic fieldwork. These foundations are set in a broader context, namely sociomaterial approaches. The way in which contemporary theorists are 'rethinking the thing' is highlighted, based on performative, diffractive and non-representational ontologies. The 'practice turn' is located within these wider, diverse, traditions, and Schatzki's practice theory is presented as an overarching framework for this book. Next, research on workplace learning is considered, highlighting the metaphor of emergence and its links to concepts of knowledge. Here Gherardi and others' practice-based studies are significant, emphasising knowing in practice and aesthetics. The chapter then shifts gear introducing the key arguments that are developed in the remainder of the book. Times, spaces, bodies and things are introduced as four essential dimensions of professional practice and learning, and then a distinctive view of professional learning in an asymmetrical and non-reversible relationship with practice is presented. Learning and practice are viewed as entangled, but analytically distinguishable, and criteria for specifying this distinction are presented.