As neuroscience strives for generalizability and equity, understanding human brain diversity across populations is crucial.

Leaf through a textbook, watch a wellness influencer, or listen in at the gym, and it can feel as though the human body has already been mapped to exhaustion. Every muscle named, every nerve traced.

Researchers in Japan built a miniature human brain circuit using fused stem-cell–derived organoids, allowing them to watch the thalamus and cortex interact in real time. They found that the thalamus ...