Ask most football people in Iceland why it's become the smallest nation to ever qualify for a major tournament, and they will point to a succession of infrastructure improvements made by the country's football association.
"There are now 30 full-size all-weather pitches...and almost 150 smaller artificial arenas that ensure youngsters at grassroots can continue to play football in winter," according to BBC Sport's Joe Lynskey. There are the 639 coaches with UEFA B licences, the second-highest level of certification for academy coaching.
And there was the 2011 appointment of Lars Lagerback to manage the national team after he qualified for five tournaments running with Sweden.
But for the team's star player, these are factors that tell only a fraction of the story.
As detailed in the book Atvinnumadurinn Gylfi Sigurdsson (Gylfi Sigurdsson, The Professional) by Olafur Thor Joelsson and Vidar Brink, the journey of Gylfi Sigurdsson began in a town called Hafnarfjordur, near Reykjavik, with a population close to 25,000.
His is a story of hard work and sacrifice, of perspiration and innovation. And one thing above all stands out—the importance of the family behind the player.
Swansea City's 26-year-old attacking midfielder was five years old when he started training at his first club, FH, in Hafnarfjordur.
Over the last decade, the team has become the most successful in Iceland, but there must have been something in the water back then. Among his team-mates in that very young side were Bjorn Daniel Sverrisson (now at Viking FK in Norway), Hjortur Logi Valgardsson (at Orebro in Sweden) and EHF Champions League handball winner Aron Palmarsson.
Olafur Mar Sigurdsson, 11 years Gylfi's senior, was a decent sportsman himself. He chose golf over football, playing in the qualifying rounds of the European Tour and competing on the Iceland team that finished fourth in the 2001 European Amateur Championship.
Olafur became Sigurdsson's first coach. "We mainly practiced technique: passing the ball, first touch and shooting ability," Olafur told Bleacher Report.
"I quickly understood that he wasn't physically strong. Gylfi is built more like a long-distance runner than a sprinter, with long and thin muscles, so he was never going to be powerful and fast," Olafur said. "For him to become a good footballer, I thought he would have to develop good technique and an understanding of the game. And he would have to be better than the others in those aspects of the game. Very early on, he was technically good."
Olafur started filming his brother when Gylfi was about seven. They would watch his exercises and work out where improvements could be made. This was 20 years ago, before the days of smartphones and YouTube.
"I don't know what people must have thought when they saw me filming a young kid playing football over and over again," he said. But he took his role seriously.
"I was trying to find every VHS tape I could find and tried to learn how to coach a young kid," Olafur said. "I did these exercises myself before I had Gylfi do them to see how it was. I almost trained like a professional myself during this process. I also put in many hours recording and cutting material of Gylfi playing with a video camera."
The videos allowed the Sigurdssons to send out footage of Gylfi to clubs in England. He visited Everton when he was 11 and a few years later went to Preston North End (for whom he played in a tournament in the United States).
At 13, Gylfi moved from FH to Breidablik, a sports club in nearby Kopavogur, which had an indoor football arena for winter play.
On Saturday mornings, Sigurdsson and his team-mates, including Alfred Finnbogason (Real Sociedad) and Johann Berg Gudmundsson (Charlton Athletic), would have extra training with Petur Petursson, a former Iceland international who scored 49 goals in 88 games for Feyenoord.
But still it was Olafur who oversaw his brother's progress. It was practically a full-time job for him, a fact recognised by their father, Sigurdur Adalsteinsson, who rented a warehouse one winter so the pair always had somewhere to play.
"We were always trying to find out what could work for Gylfi and what could help him to become a great footballer in these conditions in Iceland at the time," Olafur said.
"When there was snow outside, we were in the warehouse kicking the ball around on a concrete floor whenever we felt like it," he added.
"At some point, our father said to me that I had to choose between football and golf, and I chose golf. So he told me that I didn't have to get a summer job. I should coach Gylfi for two-three hours a day and also work on my golf game.
"When Gylfi became a teenager, our father said to him that he wouldn't get a summer job, which is what most teenagers in Iceland do. Gylfi's job was to practise his football skills."
Olafur said the family enlisted the help of an agent, Olafur Gardarsson, who had experience representing Icelandic players like Ivar Ingimarsson and Brynjar Gunnarsson.
Gardarsson told Reading about the technically brilliant midfielder and showed them some of Olafur's videos. He had a few trials and signed when he was 16.
"We had a good feeling about Reading as a club, so we didn't look at many others," Olafur said. "It was a rather small club where young players got a chance to play. Six or seven who played with Gylfi in the youth team at Reading ended up playing for the first team."
Soon after Sigurdsson joined, he was sent to Shrewsbury Town in League Two for a month on loan. Three months later, he went on loan to Crewe Alexandra, whose manager, Gudjon Thordarson, had a huge impact on his career.
"In the tough world of the lower divisions in England, Gylfi turned from a boy into a man," Thordarson said in Atvinnumadurinn Gylfi Sigurdsson. "He was the first to arrive at the training ground and the last one to leave. We had three bags with 10 balls. Gylfi always took one bag after training to practise and try to improve. If we had a game the day after, I had to go out on the training ground to tell him to stop."
Significantly, Thordarson played Sigurdsson in central midfield, where he saw a lot of the ball and found goalscoring positions as a box-to-box player. He never had pace, but stamina was always a strength.
"He was slow, but an attacking midfielder doesn't necessarily have to be very fast," Olafur said. "On the other hand, Gylfi runs a lot during games and can run from box to box for 90 minutes. He worked on the physical aspects, but he was never going to be fast."
Per Atvinnumadurinn Gylfi Sigurdsson, Thordarson thought Sigurdsson's best position was a central one, and though he has been played out wide at Hoffenheim, Reading and Spurs, it's no coincidence that Sigurdsson has been at central midfield for Iceland in the last few years.
"He's probably not the best when it comes to defending or when it comes to attacking, but when you put them all together, he is one of the best midfield players in the world today," Lagerback said in Atvinnumadurinn Gylfi Sigurdsson.
Atvinnumadurinn is the word: professional. Sigurdsson never drinks and has never smoked, and he has been working toward this moment since he was kicking a ball around with Olafur at age five. He has worked hard and shown ambition, focus and perseverance.
He has also been helped by his family, with a father who supported him and a brother who acted as a de facto coach. They will all be in France cheering him on.
"As long as he didn't get injured, I knew he would become a professional," Olafur said. "The question was how good he would become and at what level he would play. But I always believed in him."
Except as noted, all quotes obtained firsthand. Translation help and Olafur Mar Sigurdsson interview conducted for Bleacher Report by Kristijan Jonsson.