With the arrival of the Duke and Duchess of Cambridge's new baby, the order in which members of the Royal Family become king or queen - the line of succession - has changed.
So what is the order now?
Prince Charles is the Queen's eldest child so he's first in line to the throne
Next it's his eldest son, Prince William, who is second in line to the throne
He might only be a little boy, but Prince George is next in line because he's Prince William's eldest child.
And then it's the new baby girl. She's fourth in line to the throne and recent changes in the law mean that even if she has younger brothers in the future, they won't overtake her place in the line of succession.
Quiz: Guess which Royal baby's which?
The new baby has pushed her uncle Prince Harry down to fifth in line. And if the Duke and Duchess of Cambridge have any more children, they'll push Prince Harry further down the line of succession.