The highly enlarged and convoluted human brain contains approximately 86 billion neurons and a similar number of glia, resulting in extraordinary mental abilities as well as sufferings. Using human genetics and mouse models, I have elucidated (1) how a non-coding element controls cortical development in the human language area and surrounding regions, and (2) how centrosomal proteins control brain size. I will endeavor to elucidate molecular mechanisms underlying human cerebral cortical expansion and convolution, using genetically modified ferrets and human stem cell-derived cerebral organoids (in addition to mouse models) combined with powerful comparative genomics. Ultimately, I hope to understand how structural changes in the human brain have enabled acquisition of novel neurocognitive functions throughout human evolution.