Nine-year-old Niamh Clarke-Willis joined London Organising Committee of the Olympic Games and Paralympic Games (LOCOG) head Lord Coe Saturday to hit a button which launched balloons into the sky to officially open the 2012 Olympics stadium in east London, BBC said.
Around 40,000 people braved the rain and cold to participate in the opening, which included a laser light show.
LOCOG organizers said they have asked young people aged eight to 14 to register for the opportunity to open the stadium and the first 100 youngsters who applied were picked to go through the final round.
Paralympic gold medal-winning archer Danielle Brown then took aim and shot arrows at a series of spinning targets to select one young person from the audience to open the stadium.
Lord Coe said "It's a fantastic feeling. The seven years have just flown by. Tonight is only the start of the story. We want thousands of young people to be inspired to take up sport. We hope that for a few of them it will be the start of their journey. I'm grateful to everyone who came here tonight to celebrate this moment in history."
The opening celebrations were part of the British Universities and Colleges Sport Outdoor Athletics Championships and the Visa London Disability Grand Prix which were test events for the stadium venue.
The London 2012 Olympics opening ceremony of the games will take place inside the Olympic stadium at 1930 BST on Friday, 27 July, and the final day and closing ceremony will be held on August 12, Sunday.