This document discusses personal networks and how they are larger and more complex than typically thought. It summarizes some key studies that found personal networks are on average larger than what was found in earlier research. Personal networks are also fragmented across different aspects of social life and include both strong and weak ties that provide diverse information and resources. While tools like Facebook have increased contact with weaker ties, personal networks are underestimated in size due to limitations in self-reporting and how networks are defined in terms of closeness beyond just discussing important matters.