The document discusses research analyzing the social world of Twitter. It aims to characterize Twitter communities by collecting profiles, computing network metrics, and relating metrics to topics, geography, and emotions. The research finds that (1) users who broker diverse topics tend to have higher network diversity, (2) users typically have a geo span, and (3) "happy" and "sad" users tend to cluster together emotionally. Future work involves analyzing complex networks, improving tools for topic and sentiment analysis, and the urbanopticon.org project.