William Bechtel is Distinguished Professor of Philosophy at the University of California, San Diego. His research has focused on the development of mechanistic explanations in the life sciences, most recently with a focus on circadian rhythms research and extensions into systems biology and neuroscience. He is particularly interested in the complex dynamic behavior that arises in many biological mechanisms and how understanding this requires integrating accounts over multiple levels of organization (molecular, cellular, organ, and organism), often in the form of computational models. At the Center he will continue his research on the uses of diagrams in scientific reasoning not just to represent the proposed parts, operations, and organization of mechanisms but also to identify the explanatory relations that figure in mechanistic explanations and computational simulations. A major focus is on the multiplicity of ways scientists have developed to graph data to reveal these relations.