This document discusses social networks and how to harness their power for social impact. It defines a social network as a group of people connected by relationships. While networks have long existed, connectivity is growing dramatically with new technologies like cell phones and online spaces. This represents a newly dominant form of organizing. The key is to help "Reed's Law" win out over "Brooks's Law" - meaning networks should scale exponentially with more participants rather than projects taking longer. To do so requires a "network mindset" of loosely controlled emergence, strengthening connections across the network, and decentralized decision-making rather than traditional top-down control.