Mark Pfetzer of Rhode Island has scrambled up ice-coated mountains in North and South America, Asia and Africa. At age 16, he became the youngest person to climb 26,000 feet up Mount Everest, the world's tallest mountain. On that trip he coughed so hard while trying to breathe in the thin air that he broke a rib! He also survived a deadly storm that killed nine other climbers. A book that he wrote about his adventures, Within Reach: My Everest Story (Dutton), arrives in stores this month. Now 18, Mark is preparing to return to Everest for a shot at climbing to its very top--29,028 feet high. He would be the youngest person to do that too. "The mountain stays the same," Mark says of mighty Mount Everest, "but each climb is different."