Queen Elizabeth II is celebrating her 90th birthday
She met well-wishers in Windsor and lit a symbolic beacon
Gun salutes have been taking place around the UK
David Cameron led tributes in the Commons to Britain's longest serving monarch
It is not just people from the UK who have been searching Google for details about the Queen.
But it may come as a surprise which countries most searches originate from.
The top five are listed below.
#HappyBirthdayYourMajesty is currently the world's top trending hashtag on Twitter.
Image source, PA
Image source, AFP
Image source, Getty ImagesRepublic has criticised coverage being given to the Queen on her 90th birthday, including that of the BBC, on its Twitter feed, external.
The republican pressure group has said the Queen's birthday "does not warrant this kind of coverage" and that the BBC had a "duty to report, not to celebrate the royals".
Group CEO Graham Smith added that the BBC had "failed completely" to report the birthday in a way that was "fair, balanced and proportionate".
The Queen and Prince Philip have been greeting crowds as they travel around Windsor in an open-top Range Rover.
The monarch earlier unveiled a plaque for a digital walking trail in Windsor and took part in a walkabout of the town.
Range Rover modified one of its cars to allow Prince Philip and the Queen to stand in their vehicle and continue to greet the public in Windsor.
The Queen cut cake made specially for her by Nadiya Hussain, winner of the Great British Bake Off.
Nadiya earlier told the BBC she had been "really nervous" this morning but was now "trying to enjoy every moment".
Some of the 90-year-olds reportedly commented on how healthy the Queen appears.
Her Majesty was greeted at the Windsor Guildhall by fellow nonagenarians who share the same birthday.
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Children and adults have started singing Happy Birthday to the Queen as she continues to walk around the crowds that have gathered in Windsor.
She has also been collecting flowers and tributes.
The Queen is walking through the streets of Windsor - among the crowds are people who have been waiting overnight for this moment.
Her Majesty is greeted outside Windsor Castle with a deluge of flowers and well-wishers around Henry VIII gate.
The Queen has just arrived by car and has begun meeting well-wishers by Windsor Castle.
Royal gun salutes have just begun to mark the Queen's 90th birthday.
The one pictured here is taking place at London's Hyde Park.
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To see more of the tributes being paid in the House of Commons to the Queen, you can follow the BBC's politics live page here.
House of Commons
Parliament
Angus Robertson, the SNP's parliamentary group leader, has also been paying tribute to the Queen.
He said he wanted to "put on record the appreciation of the people in Scotland for the Queen".
Mr Robertson said the Queen had a "lifetime connection" with the people of Scotland.
House of Commons
Parliament
Labour leader Jeremy Corbyn told MPs that as a "relatively young whippersnapper", he is in favour of leaders from "a finer vintage".
He added: "Whatever people's views on the institution, the vast majority share an opinion that the Queen had served the country with a clear sense of public duty."
He also paid tribute to her wit, recalling the time when the Queen asked a new MP, Mildred Gordon, how she was getting on.
Ms Gordon lamented the fact that she felt she had very little power to help her constituents, to which the Queen replied "that when they find out you can't help, they all talk to me."
Hundreds of people are waiting with anticipation for the Queen to walk out of the Henry VIII gate at Windsor Castle.
Well-wishers have flocked from across the UK, and some families have come from as far afield as Egypt and Canada.
