Katherine M. Keyes, PhD, is an Assistant Professor of Epidemiology at Columbia University. Her research focuses on life course epidemiology with particular attention to psychiatric disorders, including cross-generational cohort effects on substance use, mental health, and chronic disease. She has particular expertise in the development and application of novel epidemiological methods, and in the development of epidemiological theory to measure and elucidate the drivers of population health. Sandro Galea, MD, DrPH, is the Robert A. Knox Professor and Dean at the School of Public Health at Boston University. A physician and epidemiologist interested in the social production of health of urban populations, his work explores innovative cells-to-society approaches to population health questions, with an overall aim of advancing a consequentialist approach to population health scholarship. He is a past president of the Society for Epidemiologic Research and an elected member of the National Academy of Medicine. Together Keyes and Galea have taught introductory epidemiology across various institutions for more than 15 years.