The Technology Review interviews researcher Doug Melton: "If a patient has Parkinson's disease, their dopamine-producing cells are gone. We don't understand anything about what makes those cells go away - the field is kind of stuck because you can't watch the progression of the disease. Stem cells can make neurons in a dish. Imagine you have iPS cells from a healthy person and from a Parkinson's patient. If you make dopamine neurons from both sets of cells in separate dishes, you can look at what went wrong with the diseased stem cell. The same approach will work with different degenerative diseases, such as diabetes or ALS. ... I think it will change the way degenerative diseases are studied - we'll reduce the whole process of disease to a petri dish. Within a few years, researchers the world over should have access to disease-specific cells that can be turned into cell types defective in a particular disease. ... Science clearly works best when you have a lot of bright, motivated people working on these problems. The institute has sent thousands of human embryonic stem-cell lines to hundreds of labs all over the world. We like to think that has been helpful in encouraging basic research on embryonic stem cells."