In 2010, Horan auditioned as a solo artist for British televised singing competition The X Factor.
After being eliminated as a solo performer, Horan joined four other contestants to form One Direction.
Their first single, "What Makes You Beautiful", reached number one in Ireland, Mexico and the UK.
In November 2012, they released their second studio album, Take Me Home.
Subsequently, the group got together for two weeks to get to know each other and to practice.
For their qualifying song at "judges' houses" and their first song as a group, One Direction sang an acoustic version of "Torn".
This album had a better reception than their first album, reaching number one in the UK and becoming their first album to top the UK chart.
It also reached the first spot in Australia, Canada, the United States, Ireland and New Zealand.
Following The X Factor, One Direction had been signed by Cowell to a reported £2 million Syco record contract.
His aunt discovered his talent one day when she was in the car with Niall as he started singing. As a teenager he performed at the Mullingar Arts Centre (in a fund-raiser for the local football team, the Shamrocks).
He was also bagging a support slot with former X Factor contestant Lloyd Daniels at the Academy club in Dublin.
Niall, along with Harry Styles, Liam Payne, Louis Tomlinson and Zayn Malik, formed One Direction.
Styles came up with the band name, which he thought would sound good when announcer Peter Dickson read their name out on the live shows.