A detailed map of mouse brain cell structure and connections, offering insights into how they relate to activity in the mouse brain, is revealed in a package of open access papers from the MICrONS (Machine Intelligence from Cortical Networks) consortium, published in Nature and Nature Methods. From just one cubic millimetre of mouse brain — about the size of a chia seed — around 84,000 neurons, half a billion synapses, and approximately 5.4 kilometres of neuronal wiring are traced with newly dev