Developmental science aims to understand relations between the past, present, and future. Prior emphases on deterministic predictions based on continuities in biological or psychological traits have given way to multivariate and multilevel probabilistic estimates based on environmental transactions at every level. Continuity is now seen as an epiphenomenon of stable organism-environment relations. The study of discontinuities between levels over time provides the foundation for designing interventions to improve life trajectories by changing organism-environment relations.