Advanced computing and imaging technologies enable scientists to study natural phenomena at unprecedented precision, resulting in an explosive growth of data. The size of the collected information about the Internet and mobile device users is expected to be even greater. To make sense and maximize utilization of such vast amounts of data for knowledge discovery and decision making, we need a new set of tools beyond conventional data mining and statistical analysis methods. Visualization transforms large quantities of, often multiple-dimensional, data into graphical representations that exploit the high-bandwidth channel of the human visual system, leveraging the brain's remarkable ability to detect patterns and draw inferences. It has been shown very effective in understanding large, complex data, and thus become an indispensable tool for many areas of research and practice. I will present several use cases of visualization based on new concepts and techniques that my group at UC Davis has introduced to further advance the visualization technology as a powerful discovery and communication tool.