JessicaRulestheUniverse.com

When you were a kid did your parents make you pluck out their gray hairs? What rate did they give you per piece? I got five cents. Now I have my own grays to pluck out. I can get some grays at the back of my head using two mirrors. Bruno’s had a gray-plucking service, I wonder if they still offer it.

What do scientists know about the causes of graying? Very little.

The age of graying seems to be determined by heredity, The Journal of Investigative Dermatology reported in 2005. Whites tend to gray first, often as early as their mid-30s, followed by Asians and then Africans. About half of 50-year-olds are at least 50 percent gray. So it would seem that Mr. Obama, at 47, is a little late to the graying game.

But while the arrival of gray hair is relatively predictable, how and why hair ages this way is not well understood. Unlocking those secrets could have potential well beyond vanity, leading to a better understanding of the aging process at the cellular level. Scientists even hope that by identifying the mechanism that kills hardy hair-pigment cells and leaves us awash in gray, they can develop new treatments for shutting down more troublesome cells — like those that cause skin cancer.