Elizabeth, Britain's longest-reigning monarch, was born on April 21, 1926. She became queen at age 25 and went on to serve 70 years on the throne before her death in 2022 at age 96.
Elizabeth's eldest child, her son King Charles III, kicked off remembrances for his late mom on Tuesday with a recorded video message marking the occasion.
"Much about the times we now live in, I suspect, may have troubled her deeply, but I take heart from her belief that goodness will always prevail and that a brighter dawn is never far from the horizon," Charles said, in part. "For, as a young Princess Elizabeth put it in her first ever public broadcast, age just 14, we can each play our part to make the world of tomorrow a better and happier place. It is a belief which I share with all my heart. So young or old and whatever our differences, let us therefore seek to follow this example as we make today not the marking of a milestone felt by absence but the celebration of a life well-lived and a legacy of hope as we strive together towards a better, happier tomorrow, one rooted in peace, justice, prosperity and security.
Charles ended his speech by saying, "In this I renew my own solemn pledge of duty and service to you all. God bless you, darling Mama. You remain forever in our hearts and prayers."
Charles and his wife Queen Camilla are also joining members of the royal family Tuesday in viewing designs for a planned Queen Elizabeth Memorial in London.
The memorial is set to include statues of Elizabeth and her late husband, Prince Philip, near Buckingham Palace, as well as gardens and a glass bridge representing the tiara that Elizabeth wore when she wed Philip in 1947.
Also on Tuesday, Charles and the royal family will host a reception at Buckingham Palace for the late queen's birthday.
Other tributes to Elizabeth on her birthday include the opening of The Queen Elizabeth II Garden in The Regent's Park, London, attended by her daughter, Anne, the Princess Royal.
A new national charity, The Queen Elizabeth Trust, was also announced to honor Elizabeth's decades of public service.
The Trust, launched with a $50 million endowment from the U.K. government, will aim to preserve and support green spaces and community centers, according to the Queen Elizabeth Memorial Committee, a joint body established by the U.K. government and the royal household.
The committee has also launched The Queen Elizabeth Digital Memorial as a public archive of Elizabeth's public life.