On September 11, 2001, Americans witnessed an indescribable day of terrorist attacks, with passenger planes crashing into the World Trade Center and the Pentagon, and the thwarted hijacking of Flight 93 which crashed in a rural field in Pennsylvania.
Thousands of lives were lost.
At the 10th annual memorial service at the World Trade Center site Sunday morning, native New Yorker Paul Simon sang "The Sound of Silence" as thousands gathered to reflect.
As we remember and pay tribute to those who passed in the September 11 attacks, we also honor the heroes who saved so many lives on that horrific day.
Take a look at what other celebrities had to say on the 10th anniversary of a day that will live in infamy.
Jordin Sparks, via her WhoSay account: Seeing the 9/11 Memorial light up the skyline as I flew into NYC this morning: speechless.
Kim Kardashian: My thoughts and prayers go out to all of the families affected by the awful tragedy of 9/11.
Joe Jonas: Remembering the ones lost and the ones who fought to protect us on this ten years. #NeverForget
Serena Williams: My Thoughts and prayers to all who lost loved ones on 9-11. I know the entire country is with you today. I'm playing for you today.
Holly Robinson Peete: For the loved ones of those taken on 911 and those who have given their lives in service to our country- WE SUPPORT YOU #september11
Nia Vardalos: Remembering the fear, vulnerability felt 10 yrs ago on 9/11. Hoping for safer world for my daughter.
Kylie Minogue: Love, love, love....on this day 9/11 to All The Lovers
Kirstie Alley: So many Heroes to remember.The ones who died & the ones who fought to save them...& those who fight daily to ensure our freedom. We salute U
Diddy: God Bless all who effected by 9-11.
Jake Pavelka: The heart is not judged by how much you love, but by how much you are loved by others. 9/11 Victims, America loves and remembers you!
Joel Madden: We will always remember 9/11 and those who have given their lives for us to be free. God Bless America
Ellen Degeneres: Ten years ago today, the world changed. I hope everyone finds time to remember those we lost… and to tell someone that you love them.
Soleil Moon Frye: 9/11. Sending love, light and healing on this day.
Jay Manuel: Remembering 9/11...The new memorial fountain in NYC is stunning, but I would rather have all the lives lost back! How do we heal this world?
Giuliana Rancic: Watching names being read of the victims of 9/11. Ten years later....those lost will be remembered today and always
Nathan Followill: Good morning. My prayers are with those affected by the 9-11 tragedy. I'm so thankful 4 my family & friends. Tell someone you love them 2day
Snooki: #Iwill shake a firefighter's hand. What will you do this Sept 11? Join the 9/11 Tribute Movement @911day #IWill.
Jamie-Lynn Sigler: As I head out 4 my day,knowing I'm so blessed, I say a prayer for everyone so hurt by today,and so brave every day since. A city of heroes.
Marlon Wayans: To honor our brave police force, fire fighters, victims, and the families of 9/11 I give my HOUR of TWITTER SILENCE...
Brooklyn Decker: We will never forget, the world will never forget. So proud to be an American.
Jewel: 9/11....poverty stole our golden shoes, but did not steal our laughter, heartache came to visit, but we knew it was not ever after
Haylie Duff: Will never forget 9/11. Love to the families left behind. Thankful to all the men & women who gave their lives for our freedom.
Piers Morgan: More than 90 countries lost citizens on 9/11. This was an attack on the world.
Lebron James: Thoughts and prayers to all who lost loved ones on 9-11. I know the entire country is with you today and will never forget. So thankful for this country and the great people who protect it. God Bless America!
Debi Mazar: In deep thought and prayer for victims&heroe's of 9/11.will never forget that day..
Brooke Burke: My prayers to all who lost loved ones on this tragic day. It was a close call for many. My family's story http://bit.ly/pPzZm5 #911
Jenna Dewan-Tatum: Having a moment thinking of the brave souls who lost their lives on 9/11. Live every day with purpose and share love with all..
Sara Paxton: Ten years after one of the darkest days in American History, I will be remembering those whose lives were stolen by the brutal attacks on our Country. My thoughts and prayers will be with the families who lost their loved ones. It is important to Never forget that day when all Americans stood united.
Denise Richards: My thoughts and prayers are with all the families & loved ones affected by the devastating tragedy of 9/11 We will never forget....
Jill Zarin: My prayers & thoughts go out to all the innocent people lost on #9/11. Say a prayer for the true heroes & their families! #GodBlessAmerica
Bethenny Frankel: Never forget.
(Originally published on Sept. 11, 2011 at 11:46 a.m. PT)