Google partnered with HHMI Janelia and collaborators to publish a complete wiring diagram of the male fruit fly's brain and central nervous system in *Cell*. With over 166,000 neurons and 125 million synaptic connections, this is the largest brain map by neuron count to date. The project, a decade-long effort, advances connectomics using AI and computing to build cellular-scale maps. The male fly connectome includes the ventral nerve cord, analogous to the spinal cord, expanding understanding of how the brain controls the body.

The map has been annotated and verified by human experts at HHMI Janelia and is accessible via Neuroglancer, Google's open-source visualization tool. This complements the recently released female fruit fly brain map, enabling comparison of sex-specific neural differences related to courtship and aggression, as well as individual variability.

Google's AI connectomics tools, including flood-filling networks and the PATHFINDER system, were essential for stitching electron microscope images into 3D reconstructions. Previous milestones include a 2019 automated female brain reconstruction and a 2020 verified half-brain map with 25,000 neurons. These methods continue to improve, leveraging synthetic neurons to enhance speed and accuracy toward mapping larger brains.