This tool from the Carnegie Foundation for the Advancement of Teaching examines the social structure and development of Networked Improvement Communities (NICs), highlighting their role as scientific-professional learning communities in education. It outlines how NICs bring together diverse organizations and individuals to collaboratively address complex educational challenges that cannot be solved in isolation. The paper introduces a framework for NIC development that emphasizes both technical processes and social dimensions, including shared goals, disciplined inquiry, and knowledge management. Attention is given to the organizational structures that support participation, engagement, and relational trust, as well as the cultivation of network culture, through collective identity, evidence-based practices, and shared narratives. Drawing from examples such as efforts to improve community college mathematics pathways and beginning teacher support systems, the paper illustrates the potential of NICs to accelerate improvement. Ultimately, it positions NICs as a promising model for systemic educational change while acknowledging the complexities of sustaining such networks.