CiteSpace II is a tool for detecting and visualizing emerging trends and transient patterns in scientific literature. It introduces a new approach to analyze the dynamic changes in research fields by identifying research fronts and their intellectual bases. A research front is defined as a group of concepts and underlying research issues that emerge and change over time. The intellectual base of a research front is its citation and co-citation footprint in scientific literature, forming an evolving network of publications cited by research front concepts. Kleinberg's burst detection algorithm is used to identify emergent research front concepts, while Freeman's betweenness centrality metric highlights pivotal points of paradigm shifts over time. Two complementary visualization views, cluster views and time-zone views, are designed to help users understand the structure and temporal patterns of research trends. The contributions of the approach include identifying the nature of an intellectual base through emergent research-front terms, interpreting the value of co-citation clusters in terms of research front concepts, and reducing network complexity by highlighting algorithmically detected pivotal points. CiteSpace II is implemented as a Java application and applied to analyze two research fields: mass extinction (1981-2004) and terrorism (1990-2003). The results were verified with domain experts and evaluated by examining relevant articles. The tool has practical implications for understanding the dynamics of scientific literature and identifying key trends and changes. Challenges and opportunities for future studies are also identified.CiteSpace II is a tool for detecting and visualizing emerging trends and transient patterns in scientific literature. It introduces a new approach to analyze the dynamic changes in research fields by identifying research fronts and their intellectual bases. A research front is defined as a group of concepts and underlying research issues that emerge and change over time. The intellectual base of a research front is its citation and co-citation footprint in scientific literature, forming an evolving network of publications cited by research front concepts. Kleinberg's burst detection algorithm is used to identify emergent research front concepts, while Freeman's betweenness centrality metric highlights pivotal points of paradigm shifts over time. Two complementary visualization views, cluster views and time-zone views, are designed to help users understand the structure and temporal patterns of research trends. The contributions of the approach include identifying the nature of an intellectual base through emergent research-front terms, interpreting the value of co-citation clusters in terms of research front concepts, and reducing network complexity by highlighting algorithmically detected pivotal points. CiteSpace II is implemented as a Java application and applied to analyze two research fields: mass extinction (1981-2004) and terrorism (1990-2003). The results were verified with domain experts and evaluated by examining relevant articles. The tool has practical implications for understanding the dynamics of scientific literature and identifying key trends and changes. Challenges and opportunities for future studies are also identified.