How did scientists build the entire pain pathway in a lab dish?

The answer

In 2025, Stanford researchers created brain organoids - pea-sized clumps of human brain cells grown in a lab - representing different types of brain tissue, and when placed together in a dish, they spontaneously wired up to form the entire human pain pathway. The organoids self-organized, with neurons from one organoid reaching out and forming functional connections with neurons in another, just as they do during fetal brain development. For the first time, scientists could watch how pain signals are generated, transmitted, and processed in a living human neural circuit outside the body. This breakthrough could revolutionize pain research by providing a platform to test analgesics without animal models and to study chronic pain conditions at the cellular level.