For a health segment on longevity, NBC's Today show spoke with researchers at Spectracell Laboratories, the only lab in the US that currently offers a test to assess one's telomere length. "Telomeres are structures on the tips of chromosomes that shorten as people age. Think of them like the plastic tips on a shoestring; people with shorter telomeres are more likely to develop illnesses and die earlier," NBC Chief Medical Editor Nancy Snyderman says.