News from the field of stem cell research: "researchers [report] a game-changing advance in stem cell science: the creation of long-term, self-renewing, primitive neural precursor cells from human embryonic stem cells (hESCs) that can be directed to become many types of neuron without increased risk of tumor formation. ... It means we can generate stable, renewable neural stem cells or downstream products quickly, in great quantities and in a clinical grade - millions in less than a week - that can be used for clinical trials and, eventually, for clinical treatments. Until now, that has not been possible. ... Human embryonic stem cells hold great promise in regenerative medicine due to their ability to become any kind of cell needed to repair and restore damaged tissues. But the potential of hESCs has been constrained by a number of practical problems, not least among them the difficulty of growing sufficient quantities of stable, usable cells and the risk that some of these cells might form tumors. ... [Researchers] added small molecules in a chemically defined culture condition that induces hESCs to become primitive neural precursor cells, but then halts the further differentiation process. ... And because it doesn't use any gene transfer technologies or exogenous cell products, there's minimal risk of introducing mutations or outside contamination."