As former English Statesmen and Nobel Laureate (Literature), Winston Churchill said, “True genius resides in the capacity for evaluation of uncertain, hazardous, and conflicting information.” and echoed by Nobel Prize winning Physicist Richard Feynman, “What is not surrounded by uncertainty cannot be the truth.” Visualization research has often ignored the visual representation of errors and uncertainty that accompany error and uncertainty in the experimental, simulation, and/or visualization processes. This lack can be attributed in part to the inherent difficulty in defining, characterizing, and controlling comparisons between different data sets and in part to the corresponding, as well as, verifying both the simulation results and the corresponding visualization.  In this presentation I will give an overview of uncertainty visualization.