Over the past fifty years, the U.S. government has steadily increased funding for shared research facilities known as “core facilities,” with the aim of fostering discovery, innovation and national competitiveness. Due to their place at the intersection of disciplines and research programs, core facilities are often seen as places where the fruitful exchange of knowledge occurs for the benefit of science. Yet, when picturing how such exchanges of knowledge occur, most accounts overlook the occupations ideally positioned to perform them: the scientific support staff who guide researchers’ use of the facility’s tools. Despite the extensive knowledge that members of these occupations possess of the instrumentation and techniques at the base of diverse lines of research, little research has examined how they synthesize and diffuse knowledge essential to the progress of science.This study examines the role of scientific support staff in the development and dissemination of knowledge in core facilities through a multi-year ethnographic study of four academic nanofabrication facilities, core facilities that make semiconductor fabrication equipment available to researchers from a range of disciplines and industries. Drawing on sociological theories of craft knowledge and structural complexity, the dissertation documents the ways in which scientific support staff routinely select, apply and combine enduring bodies of technical knowledge to match the diverse, shifting, and technically demanding objectives of different lines of research. The findings thereby show that scientific support staff do not simply help researchers operate intricate machines and use esoteric materials, but that in doing so, they enable users to attain a level of structural complexity in the products of their work that these users would otherwise struggle to achieve. The findings contribute to research on the changing scientific workforce, the organization of scientific work, and knowledge recombination in science-based innovation. In addition, this study extends our understanding of the role that craft occupations play in their communities, by documenting how one such occupation develops, maintains and extends capabilities fundamental to the advanced achievements of a range of fields.