Cai, L.; Song, Q.; Cao, D.; Li, Q.; Wu, W.; Xiao, Y.; Chen, X.; Huang, S.; Yang, J.; Zhang, Y.; Huang, Z.-L.

Neuron typing in intact brain sections demands 3D imaging reconciling thickness compatibility with large-area coverage--a persistent challenge for FISH-based imaging methods limited by either restricted fields-of-view (<1 mm*1 mm) or thin-section constraints (<20 um). Here we introduce oblique thick light-sheet microscopy integrated with spatiotemporal 3D localization, enabling multiplexed RNA mapping across 50 um-thick tissue sections and centimeter-scale regions. The 45 degree illumination geometry achieves optical-interference-free imaging in >100 um thick tissues during single-plane scans, while a spatiotemporal localization algorithm recovers submicron resolution by pinpointing FISH spots within volumetric excitation. This strategy reveals layer-spanning neuronal distributions and region-specific expression gradients unattainable with conventional approaches. By resolving the historical trade-off between imaging depth and spatial coverage, our platform advances whole-brain transcriptomics, simultaneously enabling 3D neuron typing, projection tracing, and connectivity analysis--capabilities critical for deciphering brain-wide cellular architectures.