Do you communicate data and information to stakeholders? This issue is Part 1 of a two-part series on data visualization and evaluation. In Part 1, we introduce recent developments in the quantitative and qualitative data visualization field and provide a historical perspective on data visualization, its potential role in evaluation practice, and future directions. It discusses: * Quantitative visualization methods such as tree maps * Sparklines * Web-based interactive visualization * Different types of qualitative data visualizations, along with examples in various evaluation contexts * A toolography describing additional data visualization tools and software, along with their major strengths and limitations. Intended as a guidance for understanding and designing data visualizations, this issue introduces fundamental concepts and links them to daily practice. This is the 139th volume of the Jossey-Bass quarterly report series New Directions for Evaluation, an official publication of the American Evaluation Association.