JENNIFER LUDDEN, HOST:
Nine-year-old Tyler Armstrong has moved on from bicycling to mountain climbing. On Christmas Eve, the American boy became the youngest person to ever reach the summit of Argentina's Mt. Aconcagua. At 22,841 feet, Aconcagua is the tallest mountain in the Americas. Last year, young Mr. Armstrong reached the summit of Mt. Kilimanjaro in Africa. After the climb, which raised money for muscular dystrophy research, Tyler Armstrong said you can really see the world's atmosphere up there. All the clouds are under you and it's really cold. Transcript provided by NPR, Copyright NPR.