The aging process can be slowed, but it's an inexorable deterioration, as our bodies stop repairing the organs we need to survive. But researchers at the University of Edinburgh have managed to regenerate at least one organ in mice by tweaking a single gene. The team targeted the thymus, an organ responsible for incubating the white blood cells — called T cells — that attack infections. The thymus is crucial in immune system development, but it's also one of the first organs to atrophy in otherwise healthy humans. As a person (or mouse) ages normally, they'll become more and more vulnerable to disease, making something like the flu potentially deadly.