Advances in genomic technology have led to marked progress in gene discovery in a number of neurodevelopmental and behavioral disorders including autism spectrum disorder and Tourette disorder. The steadily increasing pool of reliable molecular data emerging from large-scale, unbiased genetic studies is setting the stage for a revolution in the understanding of these conditions. However, the goal now of moving from genes to biology and from clarifying biology to illuminating pathophysiology remains daunting. This talk will first review recent progress in Tourette disorder and autism spectrum disorder genetics and genomics, with an emphasis on the role of de novo mutations. Then, both what recent findings suggest about underlying mechanisms as well as the challenges still facing gene-first approaches to translational science in complex disorders of brain development, will be considered.