The increasing diversity and complexity characterizing today's engineering workforce and practice requires new research on the social factors that shape ethics in STEM work. A common approach in research and teaching is to incorporate the social aspects of teamwork, diversity, and ethics into isolated lectures, separate courses, or to treat them as outcome variables. However, this project takes the perspective that ethics is interwoven into everyday STEM work not as a static outcome variable, but rather as a communication-based achievement enacted in the social processes through which STEM work is organized. It tests the hypothesis that in addition to technical, process, or industry expertise, STEM team members can cultivate ethical expertise, a form of knowledge and skills informing appropriate ways of working that is developed through situated experience. This research advances scientific knowledge by systematically investigating if and how different patterns of communication affect ethical climates and ethical behavior within vertically integrated multidisciplinary STEM teams from national and university laboratories. It identifies areas in which misperceptions or misapplication of expertise may act as a barrier to the development of ethical cultures in STEM organizations and explores the ways ethics are learned and shared through ongoing social relationships and interactions. Identifying the social and communicative factors impacting the ethical accomplishment of complex scientific work provides insight into a variety of actions and policies that universities, national labs, and industry partners can use to cultivate ethical and collaborative research climates to aid in the discovery and application of scientific knowledge. <br/><br/>The study combines interview and ethnographic data with social network analysis to examine how different patterns of communication and interaction among members of STEM teams affect their perceptions of ethics in laboratories and how these perceptions impact ethical research climates and the social structures that enable effective and ethical teamwork. Phase 1 utilizes ethnographic methods and grounded thematic analysis of interviews and observations to capture and investigate the everyday practice of participants. Phase 2 builds upon these findings and employs social network analysis to assess the interdependent relationships between the different forms of expertise present in the development of ethical climates, and their relationship to ongoing interactions among team members. Phase 3 integrates these findings and maps them onto extant literature to compare the salient features of each institution and determine the explanatory mechanisms for the cultivation of ethical climates and ethical behavior in STEM teams.<br/><br/>This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.