Complexity defines health. Now, more than ever, in the age of globalization, is this so. The Commission on Social Determinants of Health (CSDH) was set up by the World Health Organization (WHO) to get to the heart of this complexity. They were tasked with summarizing the evidence on how the structure of societies, through myriad social interactions, norms and institutions, are affecting population health, and what governments and public health can do about it. To guide the Commission in its mammoth task, the WHO Secretariat conducted a review ...