Neurodevelopmental disorders (NDDs), such as autism spectrum disorder (ASD), attention-deficit/hyperactivity disorder, and intellectual disability (ID), commonly emerge during early development and impact functioning across cognitive, social-emotional, communication, and sensorimotor domains. NDDs are complex, heterogeneous disorders that evince aberrations from cellular to behavioral levels—a likely reflection of their multifaceted etiology comprising genetic, environmental, and gene-by-environment influences. Indeed, the risk for developing both ASD and ID implicates hundreds of genes, many of which commonly converge on pathways serving various aspects of brain development (1). NDDs’ association with perturbations in early neurodevelopment raises the possibility of stratifying individuals into meaningful, biologically based subgroups within and across disorder types to improve disorder diagnosis and prognostication, as well as identification of treatment targets and monitoring of treatment responses.