The differences between men and women are well known: we think and act differently at almost every level. However, medical researchers are now realizing that those same sex differences extend to every cell in the human body. When it comes to the way our bodies fight off and process disease, sex truly does matter. WSDM strives to ensure that researchers at Stanford who are looking at disease processes are routinely asking the question of sex differences. A gender- and sex-based approach to the study of illness across the life span is critical as we seek to understand why the sexes develop, respond to, and manifest disease in very different ways. WSDM seeks to create a new paradigm for understanding, preventing, and treating the health problems of women, by physician-researchers who are trained across disciplines and across the life span.