The technique has only been tested with mice so far, but it's very promising if it proves effective with humans. Rejuvenating enough cells could steel your body against blood disorders and otherwise improve your overall health. And even if the discovery goes nowhere, it still sheds light on how the blood system works. The findings show that aging-related changes in your blood aren't due to mutations -- if they were, you'd still see the damage after the reset. Instead, it looks like epigenetics (changes in gene expressions) are responsible.