Thousands of people lined the streets of London today to take part in the Queen's birthday celebrations - but it was the monarch's great-granddaughter who was the centre of attention.
Princess Charlotte made her official debut on the balcony of Buckingham Palace as the Royal Family observed an RAF flypast to mark Her Majesty's 90th birthday.
It was the 13-month-old royal's first appearance in public since posing with the Queen and her other grandchildren and great-grandchildren for a special royal portrait in April - and featured her first ever royal wave.
The tiny gesture sent the Internet into meltdown, with hundreds of Twitter users sharing adoring posts about the 'total cutie'.
One Twitter user wrote: 'Princess George and Princess Charlotte are the most adorable things'. Another said the royal siblings were 'too precious'.
Before the fly past 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 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.
The Queen was dressed in bright green and was taken to Horse Guards Parade in a carriage alongside husband Prince Philip, who wore a large bearskin.
Prince Harry accompanied the Duchess of Cambridge and the Duchess of Cornwall in another carriage, who both looked glamorous dressed all in white.
Princesses Eugenie and Beatrice followed their grandmother's lead by opting for colourful outfits, with Beatrice wearing an orange fascinator and Eugenie modelled a feathered hat.
One of the traditions of the event is for the monarch to arrive on horseback, and although the Queen could not, Prince Charles, Prince William and Princess Anne all did so in her place.
But the conditions got too much for one guardsman, who collapsed during the ceremony and was then stretchered away by officials.
It is not uncommon for a soldier to collapse at the event, with it happening before in 2013 and 2011, while a guardsman also passed out during rehearsals for this event last month.
The reason is usually a combination of the temperature - today a balmy 22C - and the heavy uniform and bearskin hats the soldiers have to wear.
At one point, Kate gave her daughter a little kiss on the forehead, while the Prince of Wales beamed at his young granddaughter.
George chatted away happily to William. The Duke, who was wearing his red tunic uniform as Colonel of Irish Guards, crouched down and pointed out the helicopters, led by the Chinook, in the distance.
The prince, who is three next month, appeared to sneeze at one point, covering his forehead with his arm afterwards.
In excitement, he banged the top of the balcony with both hands as he watched the flypast.
Around 45 members of the royal family took to the front of the palace including the Princess Royal, Zara Phillips and husband Mike Tindall, Peter Phillips, the Duke of York, Princesses Beatrice and Eugenie, and the Earl and Countess of Wessex and their children Lady Louise Mountbatten-Windsor and Viscount Severn.
The spectacle in Whitehall honoured the Queen's enduring ties with her Armed Forces and officially marked her milestone anniversary.
Over the weekend the nation is celebrating the monarch's long and rich life that has seen her become the longest reigning and oldest monarch in British history.
Cheers from the public in the Mall greeted the Queen and Duke of Edinburgh's arrival on Horse Guards Parade - Henry VIII's former jousting yard - where an audience of thousands were seated in stands.
The crowds were treated to the sight of the royal couple in a vintage carriage, Queen Victoria's 1842 ivory-mounted phaeton, and the imposing presence of The Sovereign's Escort, mounted troops from the Life Guards and Blues and Royals.
The procession included the royal colonels on horseback - the Prince of Wales, Colonel of the Welsh Guards, Princess Royal, Colonel of the Blues and Royals, and the Duke of Cambridge, Colonel of the Irish Guards.
On the parade ground in their famous scarlet tunics and bearskins were the Coldstream, Grenadier and Scots Guards - while the Irish Guards lined the Queen's processional route from Buckingham Palace.
Watching from the Duke of Wellington's old office that overlooks Horse Guards were members of the Royal Family including the Duchess of Cornwall, Prince Harry and the Duchess of Cambridge who had arrived together in a carriage.
Kate looked chic in an Alexander McQueen coat and hat by Philip Treacy while Harry was dressed in his military uniform.
They were joined by the Duke of York and his daughters Princesses Beatrice and Eugenie.
Trooping the Colour is an important social occasion for the Guardsmen taking part, and gives their wives, girlfriends, parents and other relatives the chance to celebrate the achievements of the young men and enjoy the spectacle.
Some spectators in the stands which lined the parade ground were dressed in morning suits or smart suits, while many women wore summer dresses with wide brimmed hats.
They all rose from their seats as a mark of respect as the Queen's carriage passed by, with the monarch wearing a vibrant green coat and dress by Stewart Parvin and a matching hat by Rachel Trevor Morgan, while Philip, Colonel of the Grenadier Guards, wore a bearskin and scarlet tunic.
On her shoulder the head of state wore the Brigade of Guards brooch.
After watching the parade, the royals returned to Buckingham Palace to watch the Household Cavalry procession down The Mall, with several members of the family watching from the palace balcony.
This is Prince George's second appearance on the balcony for the annual Trooping the Colour ceremony. This year he joins the royal family to celebrate the Queen's 90th birthday. And aren't we lucky to see him again!
Today he just so happens to be wearing the same exact outfit Prince William wore at Prince Harry's Christening. Isn't that adorable.
Prince George surely takes after his father as he stands regally on the balcony along with Kate and Princess Charlotte.
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The Colour being paraded on Horse Guards this year is the flag of Number 7 Company Coldstream Guards, the unit last performed this special role in 2007.
Among those taking part today was Britain's Got Talent winner and Household Cavalry bandsman Richard Jones whose skill as a magician saw him triumph in the popular show.
As a member of the Household Cavalry band he played trombone while on horseback dressed in his gold coat.
Among the audience of thousands watching the spectacle was Second World War veteran Fergus Anckorn, 97, whose story was the focus of the serviceman's magic trick that earned him the title.
Mr Anckorn, was a prisoner of war and forced to work on the Burma Railway and the infamous bridge on the River Kwai.
He said: 'It's great to be here, I've never seen Trooping the Colour before, this week I've already been to the Japanese Embassy and Buckingham Palace.'
The 97-year-old joked about the Queen's birthday: 'I remember her being born, it was common knowledge where I grew up in Kent.'
The monarch first took the royal salute in 1951, when she deputised for her ill father George VI, and has continued receiving the mark of respect every year except 1955 when there was a national rail strike.
Her first duty was to inspect the long line of troops - wearing their famous red tunics and bearskin hats - from the Coldstream, Grenadier and Scots Guards.
As she travelled in Queen Victoria's 1842 ivory mounted phaeton carriage behind her on horseback and wearing ceremonial military uniform were the royal colonels Charles, Anne and William.
With her detailed knowledge of the ceremony the Queen cast an expert eye over the troops as she passed.
And then she was taken past the Sovereign's Escort - mounted troops from the Life Guards and Blues and Royals - the King's Troop Royal Horse Artillery, who will late fire royal gun salutes, and the Mounted Band of the of the Household Cavalry.
This afternoon the royal rowbarge Gloriana will also lead a flotilla of boats down the River Thames on Saturday to honour the Queen's 90th birthday.
Prime Minister David Cameron and wife Samantha were also at the event, smiling as they watched the festivities from front row seats.
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.
'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 that 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 (NZD$303) 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.
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'.
Born Princess Elizabeth Alexandra Mary of York on April 21 1926 - the year of the General Strike - she was never expected to be Queen.
But she has become the longest reigning and oldest monarch in British history - and now the first to reach 90.
Over the decades, Britain has undergone major transformations from technological advances such as computers and supersonic flight to developments in society and the political landscape.
During her 64-year reign the monarch has been served by 12 prime ministers from Sir Winston Churchill to Mr Cameron, while Barack Obama is the 12th US president to hold office over the same period.
In preparation for the Trooping the Colour the Major General's Review kicked off from Buckingham Palace on May 28 in a vibrant display of pomp and pageantry.
More than 1,400 officers and men took part in the first of two rehearsals for the Queen's annual birthday parade, the Trooping the Colour, on June 11.
As colossal Union Jack flags fluttered from the tree-lined streets, members of the Household Cavalry - Her Majesty's official bodyguard - paraded down with two hundred horses.