A number diverse strands have shaped the development of present-day social network analysis. These strands have intersected with one another in a complex and fascinating history, sometimes fusing and at other times diverging onto their separate paths. A clear lineage for the mainstream of social network analysis can, nevertheless, be constructed from this complex history. In this lineage there are three main traditions: the sociometric analysts, who worked on small groups and produced many technical advances using the methods of graph theory; the researchers of the 1930s, who explored patterns of interpersonal relations and the formation of 'cliques'; and the social anthropologists, who built on both of these strands to investigate the structure of 'community' relations in tribal and village societies. These traditions were eventually brought together in the 1960s and 1970s, when contemporary social network analysis was forged (Figure 2.1).