Thousands of people are gathering across the city of Liverpool to pay their respects to those who lost their lives in the Hillsborough tragedy.
The memorial service to mark the 21st anniversary of the disaster will be all-ticket for the first time - with 10,000 seats available at Anfield.
Liverpool manager Rafael Benitez said it was "such an important day".
Ninety-six Liverpool fans were crushed to death on 15 April 1989 at Sheffield Wednesday's Hillsborough stadium.
The service at Anfield begins at 1445 BST, with a minute's silence at 1506 BST.
At that time, many homes and workplaces will come to a halt to pay tribute to those who lost their lives during the FA Cup semi-final with Nottingham Forest.
The minute's silence is observed at 1506 BST because that is the time on 15 April 1989 that the referee stopped the game between Liverpool and Forest, when it became apparent something was terribly wrong.
People in Sheffield are also laying flowers at the Parkside Road memorial to remember those who lost their lives.
Mr Benitez, who is attending his sixth service, added: "Since I've been here it's always been very, very emotional.
"All the players and all the staff are always there trying to support the families, because it is a very important day for the club.
"The first time I went to the memorial service I was so impressed by what happens at this club.
"You can see the people and all the feelings. It's a poignant occasion to keep everyone remembering."
Along with Liverpool stalwarts Steven Gerrard and Jamie Carragher, the Spaniard was presented with commemorative coins to mark the disaster.
The Bishop of Liverpool, the Right Reverend James Jones, who is chairman of the Hillsborough Independent Panel, is currently overseeing the release of documents not previously made public.
After a two-decade fight, the authorities finally agreed to release more than 30,000 documents of evidence relating to the tragedy.
He said: "I know this is a very difficult and distressing time for the families of the 96 who lost their lives at Hillsborough," the bishop said.
"It is our solemn responsibility to ensure that the memory of the 96, and all those whose lives were changed for ever by those terrible events, can never be forgotten."