Harry and Meghan are expecting their first baby just five months after they married at Windsor Castle.
With news of the little one's arrival comes some important dates and big decisions – such as when is the child due and what will they be called?
Here we give you everything you need to know.
When is the baby due?
Kensington Palace has said the baby is due in the spring.
The announcement comes less than five months after Harry and Meghan married on 19 May.
That's 25 weeks and five days to be precise.
It is likely the royal couple's news was confirmed in a 12-week-scan, which usually takes place between 8 and 14 weeks of pregnancy.
This means the child was probably conceived between early July and mid-August, with the royal couple having visited Dublin in Ireland during that period of the summer.
It also means Meghan is expected to give birth in around 6 months time – which would be April 2019.
Where will they sit in the line of succession?
The new baby will be seventh in line.
He or she will be behind Prince Charles, Prince William, Prince George, Princess Charlotte, Prince Louis and Prince Harry in the succession to the British throne.
Where will the baby be born?
It is of course too early to confirm where Meghan will have her royal baby, but the Duchess of Cambridge had all three of her children at the Lindo Wing at St Mary's Hospital, Paddington.
The world's press would be gathered outside the maternity wing during each birth, as they waited eagerly for a photo of the latest addition to the royal family.
Kate would later emerge from the Lindo Wing with the baby in her arms.
Why did Harry and Meghan announce it now?
Kensington Palace shared the news on Monday, three days after the wedding of Princess Eugenie on Friday.
There have been reports that Harry and Meghan told other members of the Royal Family on the day of the ceremony.
What will the child be named?
There will be much suspense amid the royal baby fever as to what the Duke and Duchess of Sussex will call their baby, with tradition an intrinsic part of British royal life.
If Harry and Meghan go classic, something like Mary, Elizabeth or Victoria are likely names for a girl.
Philip, Charles, Arthur, Edward or James would be traditional names for boys.
But the pair are also forward-thinking royals, and the duchess has her own American upbringing to draw on.
In the US, the most popular name for a baby girl is Emma and for a baby boy is Liam.
In the UK, the most popular name for a girl born in 2017 was Olivia, and for a boy Oliver.
What maternity designers will Meghan go for?
Meghan is known to favour clothes such from brands such as Barbour and Erdem.
Her wardrobe is also known to be stocked with clothes from Wilfred by Aritzia.
If Meghan chooses to follow in Kate's footsteps during her pregnancy, she could opt for clothes from Catherine Walker, Hobbs and Jenny Packham.
What clothes will the baby wear?
When Princess Charlotte was born she was photographed outside the Lindo Wing wearing G.H. Hurt & Son knitted shawl.
While Prince George was pictured wearing a Cath Kidston tank top when he was 17 months old.
Either of those brands are possible options for Harry and Meghan's child, whose gender is of course yet to be confirmed.
Kate is also known to favour the brand Rachael Riley for George's attire.
Princess Charlotte was seen wearing a yellow jumper from John Lewis on her second birthday.
Who will the child play with?
The Duke and Duchess of Cambridge's son, Louis, is currently only five months old. Born in April this year, Louis and his new cousin will be set to be close friends with only a year between them.
Louis' sister Charlotte, aged 3, could well be scheduled in for playdates with Harry and Meghan's baby.
Sibling George, at 5, may have too big of an age gap to play with his little cousin. The future king loves helicopters and anything to do with the police, so there is a chance that if the baby shows a liking for them too then the pair could bond despite the age difference.
Harry's god-daughters Florence van Cutsem and Zalie Warren were bridesmaids aged three and two at the couple's wedding in May this year.
Close to the family and not too much older than the newest royal, the path is set for them to become the best of friends.
Meghan's god-daughters who were bridesmaids aged six and seven, Remi and Ryan Litt, might be slightly too old for them to bond closely with her child but Ivy Mulroney, who was the duchess's other bridesmaid aged four, might well be invited round for play time.
There might be too much of an age gap between Harry's godson Jasper Dyer, aged six when he performed page boy duties at the wedding, and fellow page boys Ivy's brothers Brian and John, both seven-years-old in May, for successful play dates with the young royal.
Aged four, Mia Tindall, the mischievous daughter of former England rugby star Mike Tindall and his wife Zara Tindall, an Olympic horse rider, could join the young Sussex, Louis and Charlotte for play dates.
Maud, five, is the goddaughter of Eugenie and a classmate of Prince George at Thomas' School Battersea. If George is brought along to play with his cousin, it's likely Maud will make an appearance too.
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She is the daughter of Lord Freddie Windsor and actress Sophie Winkleman, who played Big Suze in the sitcom Peep Show.
And, if newly married Princess Eugenie and Jack Brooksbank decide to have children in the coming years then the young Sussex will have yet another family friend to play with.