The U.K. has released a huge repository of children’s genomic data after sequencing blood samples from three large cohorts recruited at birth and followed across three decades. The power of the data is amplified by the large volume of longitudinal health information, biological samples and responses to surveys and questionnaires that has been provided by participating families. Before this, large-scale publicly available genome sequences were limited to adult cohorts, and the only childhood genome sequence data was from children with rare diseases.