In this paper, I discuss a research agenda on the study of human capital accumulation in the early years, with a particular focus on developing countries. I discuss several methodological issues, from the use of structural models, to the importance of measurement and the development of new measurement tools. I present a conceptual framework that can be used to frame the study of human capital accumulation and view the current challenges and gaps in knowledge within such an organizing structure. I provide an example of the use of such a framework to interpret the evidence on the impacts of an early years intervention based on randomized controlled trial.