At Mount Sinai, scientists have drawn the most detailed portrait yet of the human brain's prefrontal cortex — not as a single landscape, but as a living mosaic of individual cells, each carrying its own record of health or disease. Across nine coordinated studies, researchers paired single-cell analysis with artificial intelligence to map how genes switch on and off across thousands of cells, revealing how Alzheimer's disease and neuropsychiatric conditions take hold at the molecular level. The work matters because it reframes these illnesses not as uniform afflictions but as constellations of