Queen Elizabeth II has been England's monarch for over six decades, and when she passes it will be the first time the crown will change hands since 1953.
For the royal family, Her Majesty's passing will mean a significant move up in the line of succession.
Prince Charles is currently first in line for the throne, and he will become King of England when his mother dies.
Prince William and Kate Middleton, formally the Duke and Duchess of Cambridge, will become the Prince and Princess of Wales.
This title hold's special meaning for the couple, as it was once held by the late Princess Diana.
Currently, there has been debate around Camilla, Duchess of Cornwall's, title once her husband becomes King.
In 2005 Kensington Palace announced that Camilla would never be Queen, and would instead be known as Princess Consort.
However, many noticed that Clarence House has since removed this original notice, sparking many to believe that the palace has changed it's mind in regards to Camilla's title.
When Prince William becomes King, his title will become the King of England and Kate Middleton's will become the Queen Consort - not the Queen of England. Traditionally, women who marry a sovereign inherit the title of Queen Consort, except in very rare cases.
While the Duchess of Cambridge will symbolically take her husband's social rank and status, and hold the equivalent of Prince William's monarchical titles, she does not share his military and political powers.
By contrast, Princess Charlotte may one day hold the title of Queen of England - because she will be Queen regent in her own right. Previously, Charlotte's new brother Prince Louis would have been ahead of her in the line of succession, but the Succession to the Crown Act, finalised in 2013, signaled the end to the tradition of male precedence.