Google Research has completed a historic brain mapping project in partnership with the Howard Hughes Medical Institute's Janelia Research Campus, producing the most comprehensive connectome—a detailed wiring diagram of an organism's nervous system—ever created. The map captures the complete male fruit fly brain and central nervous system, containing 166,000 neurons and 125 million synaptic connections, published in Cell. The achievement represents a decade-long collaboration combining electron microscopy, AI-powered image reconstruction, and human expert verification. The work leverages advanced AI techniques to transform millions of two-dimensional electron microscope images into three-dimensional neural reconstructions. Google's systems use deep learning algorithms including flood-filling networks and a tool called PATHFINDER to automatically identify and trace individual neurons. By automating much of the reconstruction process, the team significantly reduced reliance on manual verification that has historically made connectomics prohibitively time-consuming and expensive. The male fruit fly connectome complements a previously published female brain map, enabling researchers to identify sex-specific neural differences and study individual neural variability. The breakthrough marks a stepping stone toward understanding larger brains. While mapping the 86 billion neurons in a human brain remains technically unfeasible today, connectomics in model organisms like fruit flies and fish offers insight into how nervous systems perceive stimuli, process information, and control behavior. Google's team is already collaborating on mapping portions of fish brains—vertebrate organisms more similar to humans—demonstrating the scalability of their AI connectomics pipeline. The open-source tools and datasets released alongside the work are expected to accelerate brain-mapping efforts across the neuroscience community.