Two Million Photos: Pete Souza Captures Obama's Presidency

Despite security concerns, the president decided to walk into the street to wave to people gathered outside the Cidade de Deus favela community center in Rio de Janeiro. As he was walking, a young boy reached out of a closed door and the president reached over to give him a fist bump on March 20, 2011.

President Barack Obama and first lady Michelle Obama hold hands as they listen to Rep. John Lewis, D-Ga., during an event to commemorate the 50th Anniversary of Bloody Sunday and the Selma to Montgomery civil rights marches, at the Edmund Pettus Bridge in Selma, Alabama, March 7, 2015.

President Barack Obama and first lady Michelle Obama together in a freight elevator at an Inaugural Ball, January 20, 2009 in Washington, DC.

President Barack Obama escorts former First Lady Nancy Reagan in the Diplomatic Room of the White House on June 2, 2009.

Secretary of State Hillary Rodham Clinton, President Barack Obama and Vice President Joe Biden, along with members of the national security team, receive an update on the mission against Osama bin Laden in the Situation Room of the White House in Washington on May 1, 2011.

Bourdain shares a meal with President Barack Obam at the Bun Cha Huong Lien restaurant in Hanoi, Vietnam in 2016. \"Total cost of bun Cha dinner with the president: $6.00,\" Bourdain tweeted. \"I picked up the check.\"

President Obama pretends to be caught in Spider-Man's web as he greets Nicholas Tamarin, 3, just outside the Oval Office on Oct. 26, 2012. Spider-Man had been trick-or-treating for an early Halloween with his father, White House aide Nate Tamarin in the Eisenhower Executive Office Building. \"I can never commit to calling any picture my favorite, but the president told me that this was HIS favorite picture of the year when he saw it hanging in the West Wing a couple of weeks later.\"

Prince George stays up past his bedtime to greet Obama and first lady at Kensington Palace on London as his father, Britain's Prince William, looks on.

President Barack Obama and his wife, Michelle, are among viewers who watched the 2009 Super Bowl in 3-D in the White House family theater.

President Barack Obama talks on the phone in the Oval Office with Russian President Vladimir Putin about the situation in Ukraine, March 1, 2014.

President Barack Obama runs down the East Colonnade with family dog, Bo, March 15, 2009.

President Barack Obama eats a nectarine following a town hall meeting at Kroger's Supermarket in Bristol, Virginia. on July 29, 2009.

President Barack Obama talks backstage with Senior Advisor Valerie Jarrett before a reception at the Hyatt at the Bellevue in Philadelphia, Pennsylvania, June 30, 2011.

Daughter of Deputy National Security Advisor Ben Rhodes, after the President lifted her in her elephant costume that she was wearing for a Halloween event at the White House, Oct. 30, 2015.

President Barack Obama fist-bumps custodian Lawrence Lipscomb in the Eisenhower Executive Office Building following the opening session of the White House Forum on Jobs and Economic Growth, Dec. 3, 2009.

President Barack Obama throws a football on the field at Soldier Field following the NATO working dinner in Chicago, Illinois, May 20, 2012.

President Barack Obama kisses First Lady Michelle Obama for the \"Kiss Cam\" while attending the U.S. Men's Olympic basketball team's game against Brazil at the Verizon Center in Washington, D.C., July 16, 2012. Vice President Joe Biden and Malia Obama look up at the jumbotron.

The President's wave aligns with a rainbow as he boards Air Force One at Norman Manley International Airport prior to departure from Kingston, Jamaica, April 9, 2015.