Out on a limb: Pioneering scientists grow monkey arms in the lab

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(CNN)In a U.S. laboratory, a monkey arm is stripped down as far as its individual cells. All that's left behind is a bare, frail scaffold.

But that's not the end of the road for this arm. The scaffold is rebuilt with infusions of cells from another being -- be it a monkey, or a human -- which grow and transform the limb.