This study presents a comprehensive connectome and inventory of the visual system in the male Drosophila optic lobe, using Focused Ion Beam milling and Scanning Electron Microscopy (FIB-SEM). The researchers developed a computational framework to quantify the anatomy of visual neurons, integrating connectivity information, neurotransmitter identity, and expert curation. They classified approximately 53,000 neurons into 727 types, with about half of these types being systematically described and named for the first time. The study also includes an extensive collection of split-GAL4 lines matched to the neuron type catalog, providing a powerful toolkit for future research. The detailed analysis of the visual system's architecture, neurotransmitter usage, and inter-regional connectivity offers new insights into the function and integration of visual information in the fly brain. This work lays the foundation for a deeper understanding of sensory processing and behavior in Drosophila.This study presents a comprehensive connectome and inventory of the visual system in the male Drosophila optic lobe, using Focused Ion Beam milling and Scanning Electron Microscopy (FIB-SEM). The researchers developed a computational framework to quantify the anatomy of visual neurons, integrating connectivity information, neurotransmitter identity, and expert curation. They classified approximately 53,000 neurons into 727 types, with about half of these types being systematically described and named for the first time. The study also includes an extensive collection of split-GAL4 lines matched to the neuron type catalog, providing a powerful toolkit for future research. The detailed analysis of the visual system's architecture, neurotransmitter usage, and inter-regional connectivity offers new insights into the function and integration of visual information in the fly brain. This work lays the foundation for a deeper understanding of sensory processing and behavior in Drosophila.