Some of this is pretty basic, for example, if you want to know the age of your kidneys, a blood test of kidney function will tell you. I have a high plaque burden, hence a higher risk of a cardiac event. I've done cardiac testing to see where I stand regarding heart function. Primarily, to give my organs the best chance of lasting beyond my current age 75, I practice healthy habits related to nutrition, exercise, stress management and sleep.

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" Wealthy software entrepreneur Bryan Johnson, 45, has one goal: To have the brain, heart, lungs, liver, kidneys, tendons, teeth, skin, hair, bladder, penis and rectum of an 18-year-old.

"To accomplish the feat, he will spend at least $2 million this year on a medical program that has more than 30 doctors monitoring his bodily functions. Led by regenerative medicine physician Oliver Zolman, 29, the team aims to reverse the aging process in every organ."