Pathways visualizes the simulation of bio-chemical networks using a Tangible User Interface (TUI) approach. In current practice in systems biology, researchers run simulation programs that model different experimental parameters such as concentrations inside cells and reaction speeds. These parameters are adjusted to discover hidden patterns in the reaction network, often by plotting the output using graphs. By adopting TUIs for visualization, we believe that researchers will be able to manipulate these parameters more easily, and also see the system-wide effects of their manipulation across the reaction network. Our first attempt is to visualize the reaction network on an interactive tabletop display. Researchers control the parameters with tangible objects and their hands, allowing them to change parameters in a continuous fashion, and focus on understanding the effects of this manipulation, rather than on programming or entering numerical values.