Modern day computer systems allow us to capture enormous datasets. In many cases this data represents a network of connections between entities, such friendship patterns in social networks, communication networks or biological pathways. Fully analyzing these massive network datasets is challenging on a number of levels and many problems remain unsolved. This book addresses the problem from the perspective of information visualization, which uses computers to generate interactive images of the data under analysis. It gives an overview of the state of the art, describes potential pitfalls and details a number possible solutions for different application areas.