Full reference: Rebay-Salisbury, K., A. Brysbaert and L. Foxhall 2014. Material cross-overs: introduction. In: K. Rebay- Salisbury, A. Brysbaert and L. Foxhall (eds), Material Crossovers: knowledge networks and the movement of technological knowledge between craft traditions. London: Routledge, 1-6. Authors’ final version (for final version, incl. images and pages, please refer to published reference above) Material Crossovers. Introduction Katharina Rebay-Salisbury, Ann Brysbaert and Lin Foxhall Knowledge networks are entangled with materials and associated technologies. This volume emphasises the significance of material objects to the construction, maintenance and collapse of human social networks of various forms, which are central to explanations of cultural contact and change. Materiality—the properties, affordances, functions and styles of different materials—is intrinsically linked to the way in which knowledge flows and technologies are transmitted. Transmission of technologies from one craft to another is one of the main drivers of innovation, whilst sharing knowledge is enabled and limited by the extent of associated social networks in place. The analysis of networks is now recognised as an important tool for understanding the way knowledge is fundamental to social, economic and political relations in both past and present-day communities. Networks of craftspeople and technological traditions across the highly interconnected world of the Mediterranean, c.1500 to 200 BCE, offer case studies through which patterns of knowledge exchange, innovation and technological change can be explored. Archaeological research, however, has often been limited to studying objects made of one particular material in depth, be it lithic materials, ceramics, textiles, glass, metal, wood or others. The knowledge flow and transfer among crafts that deal with different materials has often been overlooked. This book takes a fresh approach to the reconstruction of knowledge networks by integrating the concepts of the chaîne opératoire and cross-craft interaction. To integrate the human aspect in the production process, the chaîne opératoire is a useful methodological tool (e.g. Leroi-Gourhan 1964; Pfaffenberger 1998; Schlanger 1994). A chaîne opératoire approach considers all techno- logical and social elements of a specific commodity from the procurement of raw materials to the finished item and extends further into its distribution and subsequent sociocultural biography. Thinking through all steps of production needed from raw material to finished object, steps that are not apparent through the archaeological record may be interpolated and choices and pathways identified. Looking at ancient technological practices as they are embedded socially, incorporating beliefs and traditions and identifying choice and thus human