Network analysis systematically quantifies and visualizes relationships between actors, such as knowledge transfer or resource flow. The underlying formal concepts of graph theory make network analysis both a theoretical approach and a toolkit of formal approaches. Social network analysis is an emerging field that combines contributions from different disciplines, such as sociology, anthropology, mathematics, statistics, and, recently, physics and biology. The research approach has recently inspired several books, such as Duncan Watts's Six Degrees of Separation , Albert-László Barabási's Linked , and Nikolas Christakis and James Fowler's Connected . This entry first briefly describes the goals and historical developments of network analysis. Then, the research questions, research design strategies, data collection procedures, and basic formal data analysis mechanisms are discussed. The entry concludes with a look at recent and future developments of network analysis. Networks are social relational systems characterized by a set of actors and their social ties. They ...