Researchers have created one of the most detailed virtual mouse cortex simulations ever achieved by combining massive biological datasets with the extraordinary power of Japan’s Fugaku supercomputer. The digital brain behaves like a living system, complete with millions of neurons and tens of billions of synapses, giving scientists the ability to watch diseases like Alzheimer’s or epilepsy unfold step by step. The project opens a new path for studying brain function, tracking how damage spreads across neural circuits, and testing ideas that once required countless experiments on real tissue.