In this issue of JAMA, Männik and colleagues1 report that large (>250 kilobase [kb] pairs) structural variants in the genome, specifically deletion and duplication copy number variations (CNVs), were associated with cognitive phenotypes including intellectual disability and reduced educational achievement. These CNVs are deletions and duplications of DNA sequences in the human genome that can be considered as deviations from the normal diploid state at a given location in the genome and represent differing numbers of copies of genetic sequences. The authors also identified and examined the phenotypic consequences of genomic structural variation associated with known genomic disorders2 among individuals in whom the genomic disorders were not initially clinically recognized.