The two-hour special takes an in-depth look at her 70-year reign and details how she ascended the throne, her love story with the late Prince Philip, her family and grandchildren, the aftermath following the death of Princess Diana, and her history with the United States and world leaders, with reporting from Muir, senior national affairs correspondent Deborah Roberts and "GMA3" and "20/20" co-anchor Amy Robach. The special features interviews with those who knew and loved her most - Prince William, Prince Harry and some of her other grandchildren.