Elizabeth II: From Princess to Queen, journey of world’s oldest reigning monarch

Queen Elizabeth II, Britain's oldest and longest-serving monarch celebrated her 90th birthday on Thursday with a day at home and a short walk.
Her government and subjects are having gun salutes, fireworks and tributes in Parliament in her honor, and televised retrospectives are being broadcast of a royal life that has stretched from the Roaring '20s to the Internet age.

Britain's Queen Elizabeth II is seen walking in the private grounds of Windsor Castle on steps at the rear of the East Terrace and East Garden with four of her dogs: clockwise from top left Willow (corgi), Vulcan (dorgie), Candy (dorgie) and Holly (corgi), in this official photograph released by Buckingham Palace to mark her 90th birthday (Source: Annie Leibovitz via Reuters)

This official photograph, released by Buckingham Palace on Wednesday April 20, 2016, to mark her 90th birthday, shows Queen Elizabeth II with her five great-grandchildren and her two youngest grandchildren in the Green Drawing Room, part of Windsor Castle's semi-State apartments in Windsor England. The children are: James, Viscount Severn, 8-years-old, left, and Lady Louise, 12-years-old, second left, the children of The Earl and Countess of Wessex; Mia Tindall, holding The Queen's handbag, the two year-old-daughter of Zara and Mike Tindall; Savannah 5-years-old, third right, and Isla Phillips, 3-years-old, right, daughters of The Queen's eldest grandson Peter Phillips and his wife Autumn; Prince George, 2-years-old, second right, and in The Queen's arms and in the tradition of Royal portraiture, the youngest great-grandchild, Princess Charlotte, 11-months-old, children of Prince William and Kate Duchess of Cambridge. (Source: Annie Leibovitz via Reuters)

The queen is spending the day at Windsor Castle and will greet well-wishers on a walk through the town west of London. Hundreds have lined up hours beforehand, carrying cakes, cards, balloons and Union Jack flags.

Britain's Queen Elizabeth II is pictured with her daughter, The Princess Royal, in the White Drawing Room at Windsor Castle, in this official photograph released by Buckingham Palace to mark her 90th birthday. (Source: Annie Leibovitz via Reuters)

In this image released by the Royal Mail on Wednesday April 20, 2016, Britain's Prince George stands on foam blocks during a photo shoot for the Royal Mail in the summer of 2015 in the White Drawing Room at Buckingham Palace in London for a stamp sheet to mark the 90th birthday of Britain's Queen Elizabeth II. The image features four generations of the Royal family, from left, Prince Charles, Queen Elizabeth II, Prince George and Prince William, the Duke of Cambridge. (Source: AP)

Prince George talks to Queen Elizabeth at St. Mary Magdalene Church where Princess Charlotte was christened. (Source: AP file photo)

In this June 13, 2015 photo Britain's Prince William holds his son Prince George, with Queen Elizabeth II, right, Kate, Duchess of Cambridge and the Prince of Wales during the Trooping The Colour parade at Buckingham Palace, in London. (Source: AP Photo file photo)

Britain's Queen Elizabeth attends a service at St Paul's Cathedral in London in this March 7, 2012 file photo. (Source: Reuters)

Members of Britain's royal family (front L-R) Prince Philip, Queen Elizabeth and Prince Charles cheer during the Braemar Gathering in Braemar, Scotland in this September 1, 2012 file photo. (Source: Reuters)

Catherine, Duchess of Cambridge (L) laughs as Queen Elizabeth gestures while they watch a children's sports event in Nottingham, Britain in this June 13, 2012 file photo. (Source: Reuters)

US President Barack Obama (2nd L) and first lady Michelle Obama (2nd R) pose with Queen Elizabeth and Prince Phillip, Duke of Edinburgh before a State Dinner at Buckingham Palace in London in this May 24, 2011 file photo. (Source: Reuters)

Britain's Queen Elizabeth rides her horse in the grounds of Windsor Castle, three days after the death of her mother, in this April 2, 2002 file photo. (Source: Reuters File photo)

In Pic: Nelson Mandela stands with Britain Queen Elizabeth II on his arrival at Buckingham Palace, in London for a state banquet in his honour following his arrival in Britain. (Source: AP)

In this August 4, 1987 file photo, Diana, Princess of Wales, left, and Britain's Queen Elizabeth II smile to well-wishers outside Clarence House in London. (Source: AP file photo)

In this Thursday, November 24, 1983 file photo, the Queen and Mother Teresa look at the Insignia of the Honorary Order of Merit which Her majesty has just presented to the Lady of Calcutta, at the Rashtrapati Shavar, in New Delhi. (Source: AP Photo)

In this June 5, 1961 file photo, Britain’s Queen Elizabeth II, center, walks with American President John F. Kennedy, right, and his wife Jacqueline Kennedy, as they enter an ante-room in Buckingham Palace, London. (Source: AP photo)

In this November 24, 1954 file photo, Elizabeth II of England and Prime Minister, Sir Winston Churchill, wait at Waterloo station for the Queen mother on her return from a month in America. In front, Prince Charles and Princess Anne. (Source: AP Photo)

In this August 1951 file photo, Princess Elizabeth stands with her husband Prince Philip, the Duke of Edinburgh, and their children Prince Charles and Princess Anne at the couple's London residence at Clarence House. (Source: AP photo)

In this November 20, 1947 file photo, Britain's Princess Elizabeth leaves Westminster Abbey in London, with her husband, the Duke of Edinburgh, after their wedding ceremony. (Source: AP Photo)

In this 1942 file photo, Princess Elizabeth is pictured as "Prince Florizel", left, and her sister, princess Margaret as "Cinderella", in a pantomime the royal sisters produced in aid of the Royal Household Concerts Well Fund early in London. (Source: AP Photo)

In this June 9, 1937 file photo, then Britain's Queen Elizabeth, left, with Queen Mary, second left, and Princesses Elizabeth, nearest camera, and Princess Margaret, obscured right, driving from Buckingham Palace to the Horse Guards Parade for the Trooping of the Colour ceremony, in London. (Source: AP)