Extracting structural and functional features of widely distributed biological circuits with single cell resolution via tissue clearing and delivery vectors

•Tissue clearing and viral vectors for resolved 3D imaging of unsevered circuits.•Size-adjustable tissue-hydrogels for sample stabilization and selective extractions.•Whole-body clearing and labeling via Perfusion-assisted Agent Release in Situ.•High-throughput method for in vivo vector selection and bodywide transduction mapping.•AAV vector for transgene expression brainwide via systemic injection in the adult.