John Gurdon (1933–2025) and Ian Wilmut (1944–2023) laid the intellectual foundations for induced pluripotent stem (iPS) cell biology—Gurdon by demonstrating that a differentiated nucleus retains its full developmental potential, and Wilmut by showing that a adult somatic cell could be reprogrammed through nuclear transfer. When Shinya Yamanaka and one of us (KT) reported in 2006 that just four transcription factors could achieve the same transformation in a culture dish, that work stood on the shoulders of these scientific giants. Patient-derived neurons carrying disease mutations have yielded insights into amyotrophic lateral sclerosis, Parkinson's disease, and autism that animal models failed to provide. Brain organoids now recapitulate aspects of cortical development and interneuron migration in three-dimensional human tissue. iPS cell-derived dopaminergic progenitors might be safe and beneficial in people with Parkinson's disease.

Two priorities should define the next decade. First, iPS cell biobanks carry a heavy European-ancestry bias. Inherited genetic variation shapes neuronal phenotypes, drug metabolism, and disease susceptibility. Disease-specific collections are expanding in east Asia, including in Japan and South Korea, yet cohorts representing African, south Asian, and other populations remain scarce; recent closures of repositories have set progress back further. The priority for the next decade should be not only to address this bias, but also to foster collaboration among biobanks, so that the full breadth of human genetic diversity underpins discoveries. Second, iPS cells offer a route to reducing animal experiments in neurological research—but only if the culture reagents become affordable, as current costs exclude many research settings. Funders, manufacturers, and regulators must act together to accelerate this transition. 20 years on, the field John Gurdon and Ian Wilmut helped make possible is delivering on its promise. The next 20 years should ensure it does so equitably.