Introduction: When Life Knows No Bounds; The Quest to Beat Aging; Scientific American Presents; by Mark Fischetti, Gary Stix; 2 Page(s)

Once you see the pictures, you never forget. They elicit horror, pain and, yes, a gawking fascination. An eight-year-old boy, bald with withering limbs. A nine-year-old girl stooped like a 99-year-old woman. They suffer from progeria-premature aging-and usually meet their death by the time they reach their early teens.

What's remarkable, however, is that many of these kids are happy to be alive. Some have an uncanny emotional maturity; they are cognizant of their genetic death sentence and embrace the short time they have left. Their example suggests that knowledge of one's own mortality, even at an age when the concept is normally unfathomable, can endow life with essential meaning.