Brain connectomics using large volume electron microscopy (vEM) has been developed in a few neuroscience laboratories. This methodology allows us to analyze synaptic connections on a large scale, such as cortical columnar wiring structures. We remodeled our automated tape collecting ultramicrotome (ATUM) to control the timing of cutting to achieve reliable collection of serial ultrathin sections on slots of a grid tape. These sections were securely and quite reliably placed at similar positions within each grid slot. A transmission EM (TEM) equipped with a high-throughput EM imaging system (Blade, Voxa, USA) was used for imaging the ultrathin sections on the grid tape. The Blade-TEM system captured high-resolution (2.2 nm/pixel) TEM images of 1.1 x 1.6 mm² in size (478 gigabytes) in about 35 min, and a vEM dataset from ∼1000 serial ultrathin sections (50-nm thick sections, 514 terabytes) in about a month. Processing imaging data of such a huge size can be challenging. However, using this high-throughput EM pipeline, we have been analyzing the circuit architecture of a marmoset prefrontal cortex (PFC). Combined antero- and retrograde viral tracing revealed reciprocal projections between columnar patches within the marmoset PFC (Watakabe et al., Neuron. 2023; 111(14):2258-2273). However, their connectivity at synaptic levels remains unclear. To unravel this cortico-cortical circuit, we acquired a large TEM dataset after confocal laser scanning microscopy of PFC sections in which both axons and dendrites were labeled anterogradely and retrogradely. The results with this correlative light and EM using vEM will be reported.