Many people will be familiar with Parkinson’s disease: the progressive brain disorder that causes symptoms including tremors and slower movement, leading on to serious cognitive problems. You might not know that it’s the fastest-growing neurological condition in the world. Today it affects around 11.8 million people and that’s forecast to double by 2030. Dr Sonia Gandhi is one of the scientists working to change that trend. As Professor of Neurology at University College London and Assistant Research Director at the Francis Crick Institute, her work involves using stem cells to build models of the human brain, helping to drive the development of drugs and other therapies for Parkinson’s patients. Talking to Professor Jim Al-Khalili, Sonia explains why this destructive condition is on the rise - and the promising routes they're studying to find new ways to tackle it.