grandfather who has conquered so many challenges, and turning 80 years old, he sent us this. dolph hatfield is from washington, d.c., a father, husband, grandfather. and retired scientist from the national cancer institute. he's also a black belt in tae kwon do. he's conquered challenges throughout his whole life. he's gone skydiving, climbed kilimanjaro and el capitan. he went running with the bulls. but just a few years ago, he faced his toughest challenge yet -- complications during a surgery left it nearly impossible for him to walk. but he conquered that, too, and so when it came time to celebrate his 80th birthday this week, he had an idea and invited us along. >> thank you, david, for sharing my 80th birthday with your viewers. >> reporter: taking us 764 feet up to the world's highest bungee jump in china. dolph was ready. >> i'm ready to go. let's get it on. >> reporter: strapping him in, walking out to that ledge and down below, anxiously watching, his wife, mary, and daughter, sandy. and then, the countdown.