Resting brain stem cells hardly differ from normal astrocytes, which support the nerve cells in the brain. How can almost identical cells perform such different functions? The key lies in the methylation of their genetic material, which endowes these special astrocytes with stem cell properties. In mice, the researchers showed that experimentally induced lack of blood supply in the brain epigenetically reprograms astrocytes into brain stem cells, which in turn can give rise to nerve progenitor cells. This discovery shows that astrocytes could potentially be used in regenerative medicine to replace damaged nerve cells.