Mitochondrial Eve

In the field of human genetics, Mitochondrial Eve refers to the matrilineal "MRCA" (most recent common ancestor). In other words, she was the woman from whom all living humans today descend, on their mother's side, and through the mothers of those mothers and so on, back until all lines converge on one person. Because all mitochondrial DNA (mtDNA) is generally passed from mother to offspring without recombination, all mitochondrial DNA (mtDNA) in every living person is directly descended from hers by definition. Mitochondrial Eve is the female counterpart of Y-chromosomal Adam, the patrilineal most recent common ancestor, although they lived thousands of years apart.
It's very incredible to hear that everyone in the world can be traced back somehow to this one person. It really helps give a better sense of inter-connectedness to your fellow man/woman.