Every president since Ronald Reagan has left a note for his successor, and President Biden could be the first to write a letter to someone who is both his successor and the predecessor who left a note for him.

Joe Biden was photographed at Donald Trump's inauguration ceremony in Washington, D.C, on Monday. Carrying out the tradition, Biden and the outgoing first lady Jill Biden were at the event to pass the baton to Trump as he heads into his second term.

Former President Bill Clinton was spotted at the inauguration of Donald Trump. See pictures of the former President here.

After signing a slew of executive orders, President Trump and first lady Melania attended two inaugural balls.

Donald Trump, who overcame impeachments, criminal indictments, and a pair of assassination attempts to win another term in the White House, will be sworn in Monday as the 47th U.S. president.