Kirani James exploded on to the world stage with victory in the 400 metres final to give the tiny Caribbean nation of Grenada its first world championships medal on Tuesday.
Just two days short of his 19th birthday, James nervelessly chased down LaShawn Merritt, the defending champion, on the home straight and surged past the American just before the line to claim the gold medal in a personal best time of 44.60secs.
"It's a great feeling, but it's great just being here representing my country," James said. "I was just trying to relax and finish strong."
Merritt, the Olympic champion, came round the final bend with what looked like a comfortable lead before being beaten by James's finish.
Merritt, who returned from a 21-month ban for doping in July and set the best time of the year in the first round in Daegu, took his second world championship silver medal in 44.63.
"He's a great athlete, I just didn't have a great day," said the 25 year old. "44.60, I'll take it. I'm back."
Belgium's Kevin Borlee, whose twin brother Jonathan finished fifth in the final, claimed bronze in 44.90.
James, the third youngest men's champion at the worlds, only made his debut as a professional athlete at the Diamond League meeting in London this month after racking up many junior titles and records.
Two years ago he broke Usain Bolt's six-year old CARIFA Games 400m record and he was named his country's sportsman of the year at the age of 17 after winning the 2010 world junior title.
"He's not one of those who's cocky, he would love the attention to be taken away from him, but inside is a drive," his coach Harvey Glance told Reuters.
"He's a freak of nature. At 18 he's the first to make a final and then he goes out and wins the 400 metres. He's destined for greatness."