Psychiatric disorders have modest to high heritability, implying an important role for inherited liability carried in DNA sequences present from conception. However, it may take years or decades before this liability manifests as behaviors and inner experiences that meet criteria for a psychiatric diagnosis. In between, developmental processes unfold under genetic influence and in dynamic interaction with environments, exposures, and experiences. As a result, early life development presents a landscape of changing neural structures, evolving cognitive, socio-emotional, and behavioral repertoires, and period-specific environments. ¹ Genetic liability to psychiatric disorder is not dormant within this landscape. Rather, genome-wide association studies (GWAS) for essentially all psychiatric disorders implicate early neurodevelopmental processes that may alter developmental trajectories. ² These findings emphasize the importance of a developmental perspective in psychiatric genetics. ³ To understand the genetic etiology of psychiatric disorders and detect emerging psychopathology is to understand how genetic liability is expressed over the course of development. ⁴