Thousands of people are lining the streets of London today to take part in the Queen's official birthday celebrations - but all eyes will be on only one person later today, and it's not the monarch.
Princess Charlotte is set to make her debut on the Buckingham Palace balcony when the Royal Family observe a flypast by the Royal Air Force at around 1pm this afternoon.
It is her first appearance in public since posing with the Queen and her other grandchildren and great-grandchildren for special royal portrait in April.
Before that the Queen attended the Trooping the Colour ceremony at Horse Guards Parade, which is playing host to 1,400 soldiers, 200 horses and more than 400 musicians.
The Queen in Green: The monarch appeared dressed in near neon green alongside Prince Philip in an open top carriage to begin the Trooping the Colour ceremony
All white: The Duchess of Cornwall, left, and the Duchess of Cambridge, right, look glamorous in white as they are taken to Horse Guards Parade by carriage
Generations: The crowds were just as excited to see Prince Harry, left, as they were to see his grandparents, right
Prince William, left, centre, with Prince Charles and Princess Anne, and the Duchess of Cambridge, right, are expected to bring Princess Charlotte out on the balcony of Buckingham Palace for the first time today
The military event began at Horse Guards Parade at 10am and has been part of the monarch's birthday celebrations since the mid-1700s and will feature a fly-past by the RAF at around 1pm.
It is being screened on BBC One from until 1pm and Huw Edwards and Clare Balding will present the live coverage of the pageantry and spectacle.
The royal rowbarge Gloriana will also lead a flotilla of boats down the River Thames on Saturday to honour the Queen's 90th birthday.
Around 50 craft, including the Havengore - which carried Sir Winston Churchill's coffin at his state funeral, and Dunkirk Little Ships, will take part in the procession on Saturday as part of three days of celebrations.
Former Olympian Sir Steve Redgrave will be one of Gloriana's oarsmen, accompanied by Paralympians and ex-servicemen.
Lord Jeffrey Sterling, chairman of the Gloriana Trust, said: 'There will be two flotillas, one rowed, then alongside that the second part will be preceded by the Havengore, the boat which carried Churchill's coffin at his funeral.
'A boat from each of the decades over which the Queen has been monarch will also be taking part.
On the march: Members of the Grenadier Guards, pictured, taking part in Trooping the Colour walk in formation past Buckingham Palace
Fainted: One guardsman collapsed during the ceremony in a repeat of the 2013 event when a similar incident occurred
Stretchered off: The guardsman was carried away by officials for medical attention after likely struggling with the heat in his uniform
Smile for the camera: Camilla beams as she waves to the crowds waiting to catch a glimpse of the Queen ahead of the parade
Princesses Beatrice, left, and Eugenie, right, of York were also trooping their own colours, with the former opting for an orange fascinator
Royal wave: Prince Edward and Sophie, Countess of Wessex, were all smiles as they greeted the large crowds along The Mall
'There will be all the fire service ships. There will be something like 50 craft on the river - it will be pretty spectacular stuff.'
The Gloriana will set off east from Tower Bridge and travel upstream to Parliament, where it will be joined by other vessels before making a return journey.
The procession, which is reminiscent of the Diamond Jubilee flotilla in 2012, will perform a salute at the Tower of London, as the Tower's guns are fired.
It will coincide with the Royal Family appearing on the balcony of Buckingham Palace for the RAF flypast. 29 aircraft will mark the milestone birthday with a flypast over Buckingham Palace at 1pm on Saturday.
Tomorrow The Mall will be filled with 1,000 tables and 10,000 chairs to await guests arriving from 10am. The party will go on until 4.30pm. A £150 ticket will provide guests with lunch, entertainment, rain ponchos and suncream.
Guests will enjoy a wicker hamper lunch provided by Marks & Spencer with sandwiches, smoked salmon mousse and Pimm's and apple juice.
The event is ticketed, so those wishing to watch should go to 'live zones' in St James's Park or Green Park, although it is also being broadcast live from BBC One from 1.15pm to 4.15pm.
The street party in The Mall will be followed by a colourful, carnival-style parade, entertaining the Queen and her guests and featuring iconic moments from her life and reign.
Say cheese: The jubilant crowd was made up from people across the globe, many of whom were scrambling to take a picture
Marching band: More than 200 musicians are taking part in today's event in London alongside 1,400 soldiers and 200 horses
First in line: Crowds are building up along The Mall to see the Queen make her way to Horse Guards Parade for today's Trooping the Colour
Getting into the spirit: Some of the monarch's more passionate fans were easy to spot, such as this man dressed head-to-toe in Union Jack-themed clothes and waving flags
A royal good time: Fans are dressed in crowns and Union Jack-themed clothes to show their support for the monarch
The parade will have themes for each era, kicking off with nautical themed props and a giant puppet of the Royal Yacht Britannia to represent 1952 and beyond.
A flower power theme will dominate the '60s, while a 1980s 'neon' vibe will see Rubik's cubes and leg warmers dominating the parade.
Yesterday Prince William, Prince Harry and the Duchess of Cambridge led the throng of celebrity guests, high-profile politicians and dignitaries who turned out to a special thanksgiving ceremony in London to mark Her Majesty's birthday.
In a moving speech to more than 2,000 people who gathered inside St Paul's Cathedral, the Archbishop of Canterbury, Justin Welby, praised the way the Queen had ruled 'through war and hardship, through turmoil and change during the course of her 90 years' and asked the congregation to look back on her rule 'with deep wonder and profound gratitude'.
Others, including David Attenborough, also paid tribute to her long rule as smiled gracefully alongside her husband Prince Philip – who is celebrating his 95th birthday today – and gave fans a royal wave.
Despite the planned weekend of festivities, Prince Harry said today that the best birthday present his grandmother could receive would be a 'day off so she could lie about and do nothing'.