Researchers at the Howard Hughes Medical Institute's Janelia Research Campus and Google have completed a full "connectome" of a male fruit fly's brain, mapping every neuron and the connections between them. This follows the completion of a female Drosophila connectome earlier in 2026, giving scientists two complete brain maps to compare and a powerful new tool for studying how neural circuits produce behaviour. The achievement is also significant as a proof of concept for techniques that could eventually be applied to more complex nervous systems, potentially including those of vertebrates.

A connectome catalogues every neuron's location and every synaptic connection it forms, since this wiring dictates how sensory information is processed and turned into outputs such as memories or movement. Although the fruit fly's nervous system contains only around 150,000 neurons, the brain's neurons form over 300 million synaptic connections, a scale that required advanced imaging and machine-vision algorithms rather than the manual tracing methods used decades ago on simpler organisms such as the roundworm C. elegans. The project relied on a close collaboration between biologists, who prepared and imaged the tiny, opaque brain, and computer scientists, who developed the tools needed to reconstruct and interpret the resulting data.