Gun salutes at the tower of London mark a special occasion in Britain.
It's been 63 years since Queen Elizabeth II took the throne. The queen spent the anniversary in private, remembering her father, King George VI, who died on this day in 1952.
Queen Elizabeth is already the oldest reigning monarch, ahead of Thailand. In September she will become the longest ever reigning monarch, passing the record of her great-great-grandmother, Queen Victoria.
The queen will celebrate her 89th birthday in April.
Monarchy is the oldest form of government in the United Kingdom. The British monarchy is also known as a constitutional monarchy. This means that while a king or queen is head of state, the ability to make and pass legislation resides with an elected parliament.