his contemporary, Italian Nobel laureate Camillo Golgi.

This paper argues that there is a revolution afoot in the developmental science of gene–environment interplay. We summarize, for an audience of developmental researchers and clinicians, how epigenetic processes – chromatin structural modifications that regulate gene expression without changing DNA sequences – may offer a strong, parsimonious account for the convergence of genetic and contextual variation in the genesis of adaptive and maladaptive development. Epigenetic processes may play a plausible explanatory role in understanding: divergent trajectories and sexual dimorphisms in brain development; statistical interactions between genes and environments; the biological embedding of early psychosocial adversities; the linkages of such adversities to disorders of mental health; the striking individual variation in the strength of those linkages; the molecular origins of critical and sensitive periods; and the transgenerational inheritance of risk and protection. Taken together, these arguments converge in a claim that epigenetic processes constitute a promising and illuminating point of connection – a ‘synapse ’ – between genes and environments