The potential to create personalized digital twins of your brain and body is a hot topic in neuroscience and medicine today. These computer models are designed to simulate how parts of your brain interact and how the brain may respond to stimulation, disease, or medication. The extraordinary complexity of the brain's billions of neurons makes this a very difficult task, of course, even in the era of AI and big data. Until now, whole-brain models have struggled to capture what makes each brain unique. People’s brains are all wired slightly differently, so everyone has a unique network of neural connections that represents a kind of “brain fingerprint.” However, most so-called brain twins are currently more like distant cousins. Their performance is barely any closer to the real thing than if the model were using the wiring diagram of a random stranger. This matters because digital twins are increasingly proposed as tools for testing treatments by computer simulation, before applying them to real people.…