Summary We recently demonstrated a method called seqFISH+ that profiles >10,000 genes in single cells in intact brain samples. seqFISH+ provides 10-fold or more improvement over existing methods in the number of mRNAs profiled and barcodes detected per cell, providing a method to generate spatial atlas of cell. In this project, we will apply seqFISH+ to the aging brain at P56, 9 month and 18 month of age for both males and females. We will use the seqFISH+ data to map out cell-to-cell signaling interactions and their effects on cell fate decisions directly in situ. With the genome coverage and spatial resolution of seqFISH+, it is now possible to perform discovery-driven studies independent of scRNA-seq, allowing the interrogation of molecular processes in the aging brain directly in situ. At the same time, we will develop the computational infrastructure to understand the transition between different developmental time points at the single cell level. This highly innovative and multidisciplinary approach will allow us to systematically generate a spatial atlas of the aging brain based on anatomy and molecular identities. These collaborative efforts will allow us to break technological barriers and develop an unprecedentedly comprehensive open resource for brain research.