It's difficult to believe that 11 years have passed since terrorists attacked the U.S. on Sept. 11, 2001.
And today, much like the rest of us, some celebrities are taking time to pause and remember the horrific and tragic events of 9/11: the thousands of lives lost, the bravery and dedication of first responders and ordinary citizens and the lingering effects on our nation.
Here's what some of them are saying via Twitter.
Sarah Hyland: "As a born and raised of new yorker from the lower east side, I will #NeverForget what happened 11 years ago today. #Remember911."
Kelly Osbourne: "My thoughts & prayers are with all the family's that lost loved ones on #911! It might have been 11 years but we never forget our loved ones!"
Alyssa Milano: "God Bless America. #NeverForget911."
Josh Duhamel: "RIP to the 2,977 who lost their lives 11 years ago today. #NeverForget."
Katie Couric: "My heart remains heavy for the victims & families of those we lost on 9/11. As a city & a nation we are forever changed. #Honor9/11."
Michael Phelps: "Thoughts and prayers for those who lost loved ones... #911 #NeverForget."
Joan Rivers: "Today, we pay tribute to the innocent Americans' lives lost 11 years ago. My heart goes out to the families and friends of all the victims."
Mandy Moore: "Thoughts, prayers, love and light to those who lost ones 11 years ago. #neverforget."
Lucy Hale: "Today is Sept 11th, pledge to perform a good deed at 911day.org."
David Boreanaz: "Honor and pray for those who lost their lives today eleven years ago. Remember all the victims of 9/11. #NeverForget."
Russell Simmons: "Prayers for the victims of 9/11and their families."
Lauren Conrad: "In Remembrance: Never Forget 9/11."
Donnie Wahlberg: "Never forget! Always carry on! #NYCUSA."