This chapter conveys the importance of public health and clinical research in terms of its potential to impact the population's health. It addresses the issue of using research to improve the public's health, the laudable goal of epidemiology. The chapter reviews public health research in the twentieth century and its major successes. It presents an overview of the tension between the individual and the public, which can often conflict in public health policy. The history of mandatory vaccination can serve as a useful case study for other public health interventions that may impinge upon an individual choice. It is important for public health to recognize that its powers are not only a legal action but also a moral obligation to consider individual preferences. After a brief discussion of existing public health secondary data sources, the chapter offers a general architecture of big data for health research. The chapter concludes with the role of the individual as a population health advocate.