Crafting a visualization requires short and incremental developments, often costly both in time and effort. Agile Visualization promotes the use of the Pharo interactive development environment to significantly reduce the creation of a visualization. Pharo significantly leverages a visualization development against traditional visualization frameworks and toolkits. This book focuses on the Roassal visualization engine. Agile Visualization first presents the basic and necessary tools to visualize data. The development environment is subsequently described. The book then covers a domain-specific language framework to design and implement expressive and composable visualizations. Several applications are presented, covering epidemiological models, geographical information, network latency, and source code software analysis. Agile Visualization covers aspects that are relevant for practitioners, businesses, and academics to successfully design and implement a visualization.