The core marker of progress in psychological science is the degree to which our work enhances the welfare of people. In order to effectively enhance human welfare, we must develop comprehensive models that explain why different individuals progress along different life trajectories. Exciting theoretical accounts that describe transitional processes from gene polymorphisms through moment-to-moment behavior are beginning to emerge. These early accounts highlight opportunities to investigate specific transitional steps along that long pathway, the need to understand the universal and the contextual aspects of psychological processes, and the need to define and measure psychological constructs with more precision and clarity. It is likely that creative new research in each of these areas will bring enormous progress over the coming decade.