Modulating and recording cell activity with cell-level precision is vital to our understanding of brain function and the treatment of brain disorders, but is very challenging in intact brains. As a Packard Fellow, I will engineer methods for precise, noninvasive, and massively multiplexed monitoring and control of cells in the brain. This fundamental research will leverage our recent platform technology that allows for noninvasive modulation of neuronal activity with spatial and molecular precision. We will now take advantage of this noninvasive access and engineer barcoded protein reporters and receptors to noninvasively monitor and control large numbers of cell populations in intact brains. If successful, we will transform neuroscience by making it possible to noninvasively record the ensemble-specific expression activity and control neurons with no prior knowledge of their location or genetic identity – solely based on their cellular activity in the disease or studied behavior.