As we age, our bones become thinner, we suffer fractures more often, and diseases like osteoporosis can occur. One of the culprits is ageing stem cells in the bone marrow, which are no longer as effective at replenishing the bones. Researchers from the Max Planck Institute for Biology of Ageing and CECAD Cluster of Excellence for Ageing Research at the University of Cologne have now shown that the epigenome of these stem cells changes with age. They were able to reverse these changes in isolated stem cells by adding acetate. This rejuvenation treatment for the epigenome could become important for the treatment of diseases such as osteoporosis.