(CNN) -- He was just 4 years old when his treatment sparked international outrage. About a year later, he won an award for the world's youngest sailor. And he piloted a plane before he turned 6. Up next? Crossing the Tibetan Plateau by unicycle. Welcome to the unorthodox and controversial world of Duoduo and his "Eagle Dad." The world first met little Duoduo, as he's nicknamed, in 2012. A video surfaced of his small 4-year-old frame shivering in subfreezing temperatures. "Daddy, Daddy please hold me!" Duo cried into the camera. His tiny body was shielded from the cold and snowy New York winter only by bright yellow underwear and a pair of white sneakers. His family was in New York on vacation, but there's no time off from training when you're the son of He Liesheng. That video drew criticism and some praise from around the world. But He didn't mind. He says he knew what he was doing. "I've always felt Chinese parents spoil their only child too much," he told CNN at the time. "We don't expose them to nature enough, and they get weaker and less competitive compared to foreign children." He, who dubbed himself Eagle Dad, didn't just want his son to succeed, he wanted him to soar. "Like an eagle, I push my child to the limit so he can learn how to fly." Two years later, the duo have made good on that pledge. At their high-end apartment in Nanjing, certificates from Chinese authorities line the walls, and there are world records: There's one for the youngest person to start an investment company and one for the youngest pilot. The latter acknowledges Duoduo's 30-minute flight near Beijing at an altitude of 1,000 feet. Also posted on the wall: spreadsheets and documents that detail Duoduo's daily schedule. The precocious 6-year-old rises at 7 a.m., but only on his holiday. Normally, he wakes up at 6:30. But even the world's youngest pilot gets a day to rest. "On Sunday, I can even watch movies." Duoduo says. The energetic child, who happily speaks his mind and tears around the apartment, stands in sharp contrast to the child the world first saw crying and upset in the snow. Looking back on that day in New York, Duoduo remembers the cold, but he also remembers what came next. "When I was running nearly naked, I kept crying. And then dad gave me a hot bath." For his part, He says there's more to their story than the extreme images. Yes, he made his son run in the snow, and he also took him skiing and made him take cold baths. But there were less dramatic scenes, too. The family focuses on education, He insists, and the tough stuff has a purpose. "If a child does not go through hardship, then he cannot become strong," he explains. "That means when they are small, you should let your child struggle more, allow them to experience more, and it is good for their development." Their life isn't all struggle, though. Duoduo lives comfortably and hopes to grow up to become an entrepreneur like Bill Gates "because you can help other people and you can buy a lot of things." And what does the boy himself think of his Eagle Dad's methods? "The good side is that I can learn a lot. The bad side is that he's just too strict!"
Duoduo piloted a plane and started an investment company by age 6 .
His dad also made him stand outside in freezing cold wearing just underwear and shoes .
"Like an eagle, I push my child to the limit so he can learn how to fly," his father said .
"If a child does not go through hardship, then he cannot become strong"
(CNN) -- He was just 4 years old when his treatment sparked international outrage. About a year later, he won an award for the world's youngest sailor. And he piloted a plane before he turned 6. Up next? Crossing the Tibetan Plateau by unicycle. Welcome to the unorthodox and controversial world of Duoduo and his "Eagle Dad." The world first met little Duoduo, as he's nicknamed, in 2012. A video surfaced of his small 4-year-old frame shivering in subfreezing temperatures. "Daddy, Daddy please hold me!" Duo cried into the camera. His tiny body was shielded from the cold and snowy New York winter only by bright yellow underwear and a pair of white sneakers. His family was in New York on vacation, but there's no time off from training when you're the son of He Liesheng. That video drew criticism and some praise from around the world. But He didn't mind. He says he knew what he was doing. "I've always felt Chinese parents spoil their only child too much," he told CNN at the time. "We don't expose them to nature enough, and they get weaker and less competitive compared to foreign children." He, who dubbed himself Eagle Dad, didn't just want his son to succeed, he wanted him to soar. "Like an eagle, I push my child to the limit so he can learn how to fly." Two years later, the duo have made good on that pledge. At their high-end apartment in Nanjing, certificates from Chinese authorities line the walls, and there are world records: There's one for the youngest person to start an investment company and one for the youngest pilot. The latter acknowledges Duoduo's 30-minute flight near Beijing at an altitude of 1,000 feet. Also posted on the wall: spreadsheets and documents that detail Duoduo's daily schedule. The precocious 6-year-old rises at 7 a.m., but only on his holiday. Normally, he wakes up at 6:30. But even the world's youngest pilot gets a day to rest. "On Sunday, I can even watch movies." Duoduo says. The energetic child, who happily speaks his mind and tears around the apartment, stands in sharp contrast to the child the world first saw crying and upset in the snow. Looking back on that day in New York, Duoduo remembers the cold, but he also remembers what came next. "When I was running nearly naked, I kept crying. And then dad gave me a hot bath." For his part, He says there's more to their story than the extreme images. Yes, he made his son run in the snow, and he also took him skiing and made him take cold baths. But there were less dramatic scenes, too. The family focuses on education, He insists, and the tough stuff has a purpose. "If a child does not go through hardship, then he cannot become strong," he explains. "That means when they are small, you should let your child struggle more, allow them to experience more, and it is good for their development." Their life isn't all struggle, though. Duoduo lives comfortably and hopes to grow up to become an entrepreneur like Bill Gates "because you can help other people and you can buy a lot of things." And what does the boy himself think of his Eagle Dad's methods? "The good side is that I can learn a lot. The bad side is that he's just too strict!"
youngest sailor. And he piloted a plane before he wanted him to soar. "Like an eagle, I push my child to the limit so he can learn how to fly." child does not go through hardship, then he cannot become strong," he explains. "That means