The reason why our hair turns gray...

http://www.sciencedaily.com/releases/2009/02/090223131123.htm

Pretty interesting. Apparently as we age there is a buildup of hydrogen peroxide in our cells which prevents Melanin production. There are enzymes that typically break up hydrogen peroxide but as we age there are fewer and fewer of them and so the hydrogen peroxide builds up.

So...this means we may no longer have to dye our hair if scientists find a way to increase the enzymes that help break down Hydrogen Peroxide and stimulate Melanin production!