New research suggests it is possible to slow or even reverse aging, at least in mice, by undoing changes in gene activity—the same kinds of changes that are caused by decades of life in humans. By tweaking genes that turn adult cells back into embryoniclike ones, researchers at the Salk Institute for Biological Studies reversed the aging of mouse and human cells in vitro, extended the life of a mouse with an accelerated-aging condition and successfully promoted recovery from an injury in a middle-aged mouse, according to a study published Thursday in Cell.