Royal Baby: What does the future hold for the princess?
She will be one of the most recognised youngsters in the world, but what will the royal baby's childhood be like and what will her future have in store?
The new addition to the royal family will grow up at the very heart of the monarchy, surrounded by living history and with a great-grandmother who is head of state.
But with three generations of monarchs - Elizabeth II, the Prince of Wales and the Duke of Cambridge - between older brother Prince George and the crown, the prospect of being the sibling of a sovereign is a long way off.
William and Kate will do their utmost to give their new daughter as normal an upbringing as possible - despite being one of the Windsors.
William has often spoken of how important it was to be treated like everyone else. He treasured the time he spent away from the media at university and in the armed forces.
Kate too, although also from a wealthy background, has been praised for her down-to-earth approach and, unlike William, has the perspective of what a non-royal childhood is like.
But there is no escaping the privilege that life as a member of the royal family will bring.
The princess's central London home will be Kensington Palace's Apartment 1A, which used to belong to Princess Margaret. It was refurbished at a cost of £4.5 million (€6 million) to the taxpayer and with a big, private walled garden, there is plenty of space to play outside, as well as some 20 rooms to explore.
William and Kate also have a 10-bedroom Georgian Grade II-listed house - Anmer Hall on the Queen's Sandringham estate - in Norfolk.
It is expected they will use their country retreat more and more with William having started his job with the company that runs the East Anglian Air Ambulance.
A private education beckons, as well as an elite nursery. It might be that the Duke and Duchess choose a school close to Anmer Hall instead of Kensington Palace, depending on where William sees his long-term future.
As a teenager, a stint at boarding school is likely. The princess could follow in Kate's footsteps and be sent to Marlborough College in Wiltshire .
William calls his father "papa" and called his mother "mummy". There will always be a nanny on the scene as is customary for royal children. The family's full-time live-in nanny is Spanish-born Maria Teresa Turrion Borrallo, who trained at the prestigious Norland College. Help from housekeepers and aides will also be the norm.
The new princess and George will quickly get used to their parents heading off on official engagements or royal tours. William will also be flying both day and night shifts for East Anglian Air Ambulance, meaning the siblings will have to be careful not to wake their father up if he is on a stint of nights.
Royal protection officers will always be close by, but the Duke and Duchess will strive to make up for the lack of freedom that royal childhoods can sometimes provide.
The princess's milestones - leaving hospital after being born, her christening and her first public engagement - will be covered in minute detail by the media. The Duke and Duchess will, as with George, periodically release photos of their second born to encourage the press to avoid using paparazzi shots instead.
The family already has its first pet - a black cocker spaniel called Lupo. The baby will also have to get used to the Queen's beloved corgis and dorgis - a cross between a corgi and a dachshund.
Kate tends to take an annual winter break on the Caribbean island of Mustique with her family and summer holidays will often be spent with the family in the Scottish countryside at Balmoral - only for this youngster, grandpa will also be the Prince of Wales and their great-granny the Queen.
Royal children greet the Queen with a kiss on both cheeks and a bow or a curtsey.
Christmases will partly be at Sandringham in Norfolk with the royals, at Anmer Hall or with the Middletons in Berkshire, and trips to Buckingham Palace and Windsor Castle will expose the youngster to opulent surroundings.
Royal children also get to play in the miniature Welsh cottage Y Bwthyn Bach - The Little House - which is fully furnished and has a kitchen and is set in the grounds of Windsor's Royal Lodge.
The tiny, whitewashed thatched cottage, recently redecorated by Princess Beatrice, was given to the Queen for her sixth birthday from the people of Wales and has been used as a play den by royal children for more than 80 years.
Gifts from heads of state across the globe will be sent to the princess, in the early days, and on significant birthdays.
In 2014, George was showered with 774 official gifts - more than 600 of them during his tour of Australia.
Prince Harry is already a doting uncle to George and the Middletons will play an important part in the baby's life. The Duchess is particularly close to her family - her mother Carole, father Michael, sister Pippa and brother James.
Privacy will be paramount as William and Kate attempt to protect their growing family from the full glare of the media spotlight. The royal youngster will cultivate a trusted inner circle of friends.
If William and Kate can face a long-haul flight with two children - albeit with a nanny and staff in tow - the baby could join them on an official tour overseas, just like George did when he was nine months old.
As the princess grows older, she can expect to be prepared for her future role supporting the monarchy. She will be advised on how to conduct official engagements and how to best deal with the media.
Royal children also often appear on the palace balcony for the Queen's Birthday Parade, Trooping the Colour, as well as witnessing historic occasions first hand such as royal weddings and even coronations.
William was about to turn two in 1984 when he stood between his older cousins Zara and Peter Phillips to watch the Trooping flypast. A year later in 1985, Prince Harry made his first appearance at the Queen's Birthday Parade when he was only nine months old.
Charles was present in Westminster Abbey for his mother's coronation when he was just four years old.
Church services will also be familiar - the Queen is the Supreme Governor of the Church of England.
A stint in the armed forces has been the norm for royal boys especially spares to the heir, but the last princess born to a future sovereign - Princess Anne - did not take on any formal training with the military nor sign up to the armed forces, although she has a long association with the military and numerous honorary appointments.
The Queen however, as Princess Elizabeth, joined the Auxiliary Territorial Service in 1945.