Wouldn't you like to know how to prevent your body from aging badly? The original YOU book showed how bodies work in general, and YOU: On a Diet explained how bodies lose weight and stay fit. Now in YOU: Staying Young, Drs. Michael Roizen and Mehmet Oz illuminate the mysterious mechanisms with a lively metaphor -- the modern city. What differentiates a vibrant and thriving city that ages gracefully from one that is worn down and rusted out? Despite genetic differences, which are like the geography upon which the city is built, cities age differently because of the way residents treat their education system (stem cells), power plants (mitochondria), electrical grids (brains), transportation routes (blood vessels), and landfills (fat). You -- as mayor, resident, and street cleaner -- have the power to balance your biological budget to ensure a life that's both long and strong. Thankfully, just as cities can invest in renewal and improving their repair processes, so can you.