Life course research on health and disease has reached a new stage in exploring the social-to-biological transition. Large longitudinal datasets containing sociodemographic and socioeconomic characteristics, self-reported health assessments, psychological and biological data are coming into maturation and being made available to researchers. Some examples are the Survey of Health, Ageing and Retirement in Europe (SHARE), the UK Household longitudinal study (Understanding Society), The Longitudinal Aging Study Amsterdam (LASA), and linked registry data sets (particularly in Scandinavia). Consequently, questions around how environmental factors (in the broadest sense including social, psychosocial, behavioural, physical, etc.) lead to biological alterations over time can now be investigated on a wider scale, and in a variety of contexts and disciplines. Such work might also lead to a better understanding of the social structure of such social-to-biological mechanisms across the life course. The field of life course research is interdisciplinary by construction, stemming from different traditions. Since the 1990s, life course research on health topics developed in parallel within the fields of demography, such as in Wunch et al.’s (1996) work on unfavourable life course states and mortality; in epidemiology, where the importance of childhood circumstances for future health was highlighted by Mann et al. (1992); and in sociology via pivotal research on intergenerational social mobility and transmission (Erikson and Goldthorpe 1992, 2002). An interdisciplinary field of life course research has emerged from collaborations between these disciplines and others (Richter and Blane 2013). Given these strong traditions, life course research is well placed to establish both social and biological plausibility in hypothesis testing (Mayer 2009). While the literature has now established the associations between measures of the socioeconomic environment and subsequent morbidity and mortality, the specific pathways along which these associations are likely to operate need to be disentangled. A growing body of research hypotheses on the specific pathways that may operate between different environmental factors and biological embodiment can be identified and tested, informing deductive methods and the rejection of hypotheses or formulation of new ones (Blane et al. 2013). Recent examples of this type of research can be found in a previous issue of this journal. Hypotheses were put forward on central-nervous-system-mediated (or psychosocial) mechanisms around the development of cancers from early Michelle Kelly-Irving is a social epidemiologist working for the French institute for health and medical research (INSERM). She is based at a research unit in Toulouse, in the South West of France and her main research focus is on the social determinants of health inequalities from early life onwards. Silke Tophoven is a sociologist and research associate at the Institute for Employment Research in Nuremberg, Germany. She is interested in research on the relationship between work and health, with a special focus on women and ageing societies. David Blane has a background in medicine and sociology. He is professor emeritus of Imperial College London and professorial research associate of University College London. His research interests include social class differences in mortality, life course studies and social gerontology.