"Every now and then you have a moment of realisation when you get goosebumps and think, 'I am literally the luckiest person in the world," says Niall Horan.
Mullingar, County Westmeath, Ireland
It's hardly surprising that the pop singer has to pinch himself sometimes. In less than three years he has gone from dreaming about selling-out arenas to doing just that as one fifth of the world's biggest boy band...
Niall James Horan was born in County Westmeath, Ireland on 14 September 1993. When he was five his parents divorced and Niall and his older brother Greg decided to live with their dad so they could also stay close to their friends.
He attended Coláiste Mhuire, a boys' Christian Brothers school – but when he wasn't studying, he was working hard on his music. An accomplished guitar player, Niall has been honing his talent since he was 11-years-old, and in his free time liked to sit and write songs.
Niall was 16 when he went along to the auditions for the seventh series on the X Factor in Dublin. The confident teen drew a mixed response from the judges with his rendition of Ne Yo's So Sick, with Cheryl Cole voting not to send him through.
Luckily for Niall, Louis Walsh, Simon Cowell and guest judge Katy Perry disagreed and decided to give him another chance.
For the bootcamp round, he performed Champagne Supernova by Oasis, but failed to make it through. Then he was thrown a lifeline and invited to form a boy band with Harry Styles, Liam Payne, Zayn Malik and Louis Tomlinson.
Now a member of One Direction – Niall had jokingly suggested the boys name themselves Niall and the Potatoes – he was back in the competition, and the group progressed through the show, eventually coming third behind Rebecca Ferguson and winner Matt Cardle.
It was the start of a meteoric rise that not even mentor Simon Cowell could have predicted.
After signing to Syco Records, 1D released their debut single, What Makes You Beautiful, in September 2011. It debuted at No. 1 in the UK charts, the most pre-ordered Sony Music Entertainment single in history. Then the boys set their sights on the US.
Their first album, Up All Night, was released globally at the start of 2012. It became the fastest-selling debut album in the UK and topped the charts in no less than 16 countries, including America.
Incredibly, the boys had become the first British group in US chart history to enter at number one with a debut album.
One Direction-mania is showing no sign of slowing. The band have picked up Brit and MTV awards, performed at the Olympics closing ceremony in London, embarked on two huge tours, sang for the Queen and headlined a sold-out show at New York's Madison Square Garden.
And the biggest star of all, as far as the US is concerned, is Niall. The Irish star is the most popular member of 1D with American fans, his charm and cheeky smile proving to be completely irresistible across the pond.
He is also a big hit with his peers. A self-confessed 'Belieber', Niall has hung out with fellow chart-topper Justin Bieber – he reportedly screamed when Justin started following him on Twitter – and is Jesse J's favourite 1D member.
He also counts British singer Tulisa amongst his friends. "Niall is manic… he's got so much energy and he's constantly in fun mode," she has said of the star. "Whenever he's around he's got something to talk about, he cheers you up and that's why so many people hang out with him."
Someone who clearly agrees is Demi Lovato. The X Factor USA judge has been linked to Niall since September 2012 after meeting him at the MTV awards, and has sent him a number of messages on Twitter.
"All of the One Direction guys are great – but there is something a little special about him," the singer, 20, reportedly said in February 2013.
"Niall is really one of the most fun people to be around… He can make light of the most serious situations – and every girl needs somebody like Niall in their life. I know when a text come through from Niall there is a great chance it is going to make me laugh out loud."
Her comments came hot on the heels of Niall's reported split from model Amy Green. While their relationship was never confirmed, they were photographed on a number of occasions and were thought to have been dating since October 2012.