PROJECT SUMMARY/ABSTRACT The human brain exhibits profound diversity in biological function and vulnerability to disease. Despite the biomedical and cultural importance of inter-individual variation, we know relatively little about its underlying cellular and molecular substrates. In this work we will leverage new technologies in single-cell and spatial genomics to construct an Atlas of Human Brain Cell Variation. We will analyze tens of millions of cells from more than 200 people by single-nucleus RNA-seq and single-nucleus ATAC-seq, and a subset of these by spatial transcriptomics. Analysis of these data will seek to understand: the static versus dynamic molecular and spatial features of each cell type; the ways in which human genetic variation shapes the molecular repertoire of each cell type; and the constellations of cellular and molecular features that co-vary, appearing together in the same brains. We seek especially with this work to understand the functional connections between these phenotypes and: (i) the gene regulatory processes that drive and shape it; (ii) genetic variation associated with brain diseases; and (iii) structural brain variation measured in hundreds of neuroimaging studies. The project will deliver an essential data resource for cellular, molecular, genetic and translational neuroscience – while expanding our understanding of the ways the human brain varies across different people.