Thousands of people are heading to Manchester for a tribute concert remembering the lives lost in the 22 May attack.
One Love Manchester is raising money for those affected by the suicide bombing at the end of Ariana Grande's performance at the Manchester Arena.
She is returning to the city, joined by stars including Justin Bieber, Coldplay, Take That and Katy Perry.
The star also tweeted on Sunday that she was "praying for London".
The Manchester attack killed 22 people - including children and teenagers who saw the show as well as parents arriving at the arena to pick them up at the end of the night.
Who's playing at One Love Manchester?
Ariana Grande is going to be performing, having said she wanted to return to the "incredibly brave city" to spend time with her fans, and to "honour and raise money for the victims and their families".
She's bringing a host of stars with her - Miley Cyrus, Justin Bieber, Katy Perry, Coldplay, Usher, Pharrell, Little Mix, Robbie Williams, Black Eyed Peas, Niall Horan and Take That are all on the bill.
How many people are going?
The Old Trafford cricket ground has a 50,000 capacity and tickets sold out within 20 minutes when they went on general sale.
Some tickets were set aside for fans at the original concert, who were promised free entry. Ticketmaster said 14,200 tickets were being held for them.
People have been asked not to bring bags, "for speed of entry" and will be searched as they enter the grounds.
Greater Manchester Police said there would be additional security in place following the London attack. Armed police will be at the gates of the venue.
Where can I watch or listen to it?
- In the UK, the three-hour show is going to be broadcast on BBC One and streamed live on the BBC iPlayer. The coverage, broadcast from 18:55 BST to 22:00 BST will be presented by Sara Cox and Ore Oduba, with Nick Grimshaw and Anita Rani hosting from backstage and in the crowd.
- On radio, coverage will run from 18:30 BST to 22:00 BST. BBC Radio 1, BBC Radio 2, BBC Radio 5 Live and BBC Radio Manchester will join together to simulcast a programme hosted by Scott Mills, Jo Whiley, Phil Williams and Becky Want. They will broadcast live from within Emirates Old Trafford Cricket Ground, with build-up to the gig from 18:30 BST and 19:00 BST. All four presenters will then provide commentary from 19:00 BST onwards.
- Outside the UK, broadcasters in at least 38 countries will screen the show live, despite the time zone differences. TV networks in China, the US, Brazil, France, New Zealand, Canada and Australia will broadcast the show.
Full details are here.
What is it raising money for?
Proceeds will go to the We Love Manchester emergency fund, which has been set up by Manchester City Council, in conjunction with the British Red Cross. Organisers expect at least £2m to be raised from the event.