This chapter examines eleven regions in the United States in the 1980s and 1990s that were all rich in resources—ideas, money, and skills—which might have led to the formation of life sciences clusters. Yet only three of the regions—the San Francisco Bay Area, Boston, and San Diego—developed into robust industrial districts for biotechnology. Most research on the emergence of high-tech cluster samples on successful cases and traces backward to find a developmental pattern. In contrast, rather than read in reverse from a positive outcome, the chapter builds networks forward from their early origins, revealing three crucial factors: organizational diversity, anchor tenant organizations that protect the norms of a community and provide relational glue across multiple affiliations, and a sequence of network formation that starts with local connections and subsequently expands to global linkages.