Prince William reacts to the death of his 96-year-old queen.

[Prince William and Kate Middleton accompanied Prince George, Princess Charlotte and Prince Louis to a preview of their new school, Lamoureux.

But Thursday turned out to be the most somber day in the lives of all members of the Royal Family: Her Majesty the Queen died at the age of 96, and today William released a statement honoring the woman who was not only the Queen, but also his grandmother and great-grandmother.

"On Thursday, the world lost an extraordinary leader whose devotion to country, kingdom, and Commonwealth was absolute," he wrote on Instagram at his newly launched @princeandprincessofwales with wife Kate. 'Much will be said about the meaning of her historic reign. But I lost my grandmother. While I am saddened by her passing, I am also incredibly grateful. I have enjoyed the Queen's wisdom and reassurance through my fifth year."

On Thursday, while Kate remained in Windsor for George, Charlotte, and Louis' first day of school, William hurried to Balmoral to be near his grandmother. William joined his father, King Charles III, his brother Prince Harry, and all of Her Majesty's children at a summer retreat in Scotland.

"My wife has had her guidance and support for 20 years," William's statement continued.

"My three children were able to vacation with her and create memories that will last a lifetime."

With the Queen's death, William is now the first in line to the throne after his father Charles, the King.

"She was by my side at my happiest moments. 'And she was by my side in the saddest days of my life. I knew this day would come, but it would be some time before life without Granny would truly feel real. I am grateful for the kindness she showed my family and me. And I thank her for the example of service and dignity in public life on behalf of my generation.

After her death, William and Kate were given the new titles of Prince and Princess of Wales and Duke and Duchess of Cornwall.

"My grandmother famously said that grief is the price we pay for love," William's statement concluded.

"All the grief we will feel in the coming weeks will be a testament to the love we felt for our extraordinary Queen. I want to honor the Queen's memory by supporting my father, the King, in every way that I can."

William's statement concluded.