Moments of silence have been held for the victims of September the 11th.
Exactly 10 years after the attacks, Americans gathered to grieve where the twin towers of the World Trade Centre once stood.
The current and former US presidents were there to hear the names of the victims read out.
For the first time, relatives saw the newly-finished 9/11 memorial, which carries the names of the victims.
Moments of silence were held to mark the exact times when three planes hit the twin towers and the Pentagon, and another crashed in Shanksville after passengers fought back against the hijackers.
Police were on high alert for what they said was a credible but unconfirmed threat of an al Qaeda plot to attack the US on the 10th anniversary.