Oprah Winfrey, Paul McCartney, Stevie Wonder and Barack Obama lead the tributes to the music legend.

The rapper himself introduced the former US president at a presidential campaign rally in Detroit.

The former president also made his debut on the campaign trail on behalf of the Democratic nominee.

An American artist whose work adorned the White House features in a new exhibition in Cambridge.

The Obamas opted to use jokes, not dark and ominous warnings, in their takedown of the Republican candidate, writes North America editor Sarah Smith.

The former president and first lady aim jokes at Donald Trump - and rapper Lil Jon gets delegates on their feet.

The couple lauded Kamala Harris but urged their party members to "get to work" if they wanted to defeat Donald Trump.

Moments after the Obamas left the stage, activists in the arena gave their reaction to the speeches.