z-scan through the hippocampus and 3D-rendered model. Left, Two-photon in vivo imaging through the hippocampus starting at the top of the stratum oriens (0 μm) down to the granule cell layer of the dentate gyrus (700 μm). Right, 3D reconstruction of the z-scan. SO, Stratum oriens; SP, pyramidale; SR, radiatum; SLM, lacunosum moleculare; SM, moleculare; GC, granule cell layer.