The variability of demographic phenomena is a well-acknowledged fact: fertility, mortality and the morphology of migration have evolved at a different pace in different countries of the world, with varying effects on the population age structure. While it is difficult to pinpoint the impact of these variations, the social challenges they pose are immense. They must be understood and measured so that appropriate action can be taken to address these challenges. This international young researchers' conference aims to tackle the new issues raised by demographic transformations in the social environment, and to accompany these increasingly complex changes through demographic, sociological, anthropological, geographical, economic, epidemiological and historical analysis. This call for papers is constructed around three themes that are open to all disciplinary and methodological approaches.