Virtual worlds research is about using interactive three-dimensional computer graphics for better understanding the real world around us. Towards this end I will introduce the area of virtual reality and demonstrate its applicability in helping us understand and solve real-life problems whose domains range from the scale of a few angstroms to several hundreds of meters. This process of building tools to help solve problems in various application domains through the virtual reality technology is a deeply exciting one and explores research problems at the interface of graphics, algorithms, human-computer interaction, and the respective application domains. The current worldwide research effort in virtual environments can be organized into four main areas -- creating and managing virtual models, increasing realism, increasing interactivity, and designing intuitive user-interfaces. The virtual reality research group at Stony Brook is working on all four of the above. Our driving problems are architectural walkthroughs, mechanical CAD flythroughs, rational drug design, and financial information visualization. I will discuss these applications and outline some of our ongoing research in these areas.