Interactive visualizations leverage human visual processing and cognition to increase the scale of information with which we can effectively work. However, most visualization research to date focuses on a single-user model, overlooking the social nature of visual media. Visualizations are used not only to explore and analyze, but to communicate findings. People may disagree on how to interpret data and contribute contextual knowledge that deepens understanding. Furthermore, some data sets are so large that thorough exploration by a single person is unlikely. Jeffrey Heer from the University of California, Berkeley, presents a number of novel visualization techniques in this University of Washington Computer Science and Engineering program. (Series: CSE Colloquia - 2008)