Queen Elizabeth II becomes Britain's first ever monarch to mark her Sapphire Jubilee today.
It's been 65 years since she became Queen following the death of her father King George VI.
As Britain's longest reigning sovereign, this is a milestone in her reign that the United Kingdom has never seen before with any other monarch.
To mark the occasion Buckingham Palace re-released a photograph of the Queen wearing distinctive sapphire jewelry.
The picture was taken by the photographer David Bailey in 2014 for the GREAT campaign, a publicity campaign to promote Britain around the world.
In the photograph The Queen is wearing a suite of sapphire jewelry given to her by King George VI as a wedding present in 1947.
Her father died in 1952. Princess Elizabeth, who was 25, was in Kenya on a royal tour with her husband Prince Philip at the time.
To mark the day gun salutes are being fired in Green Park and at The Tower of London.
But there are no grand national celebrations planned for the Sapphire Jubilee.
On Sunday her majesty was given flowers by well-wishers in Norfolk after she attended a church service at St Peter and St Paul in West Newton.