Rio 2016 Olympic Games: Day 4, as it happened
Team USA's Michael Phelps picks up his 21st Olympic gold while Team GB land two more silver medals in the pool
Gold medals and shock defeats... Check out all the highlights from day four right here - and find out what to watch today.
Michael Phelps wins his 21st Olympic gold medal
The 31-year-old American swimmer is already the most decorated Olympian of all time, and Phelps added to his impressive collection yesterday, winning the 200m butterfly before helping the men's 4x200m freestyle relay to victory.
Despite his wins, he's not taking it easy just yet. The American will also be trying to add to his gold tally when he goes in the 4x100m medley relay and 200m individual medley later this week...
Serena Williams is knocked out of the women's singles in shock defeat
The world number one lost in the third round, beaten by Ukrainian Elina Svitolina. After being defeated in doubles alongside sister Venus on Sunday night Williams, who won Wimbledon – her 22nd singles Grand Slam title – last month, is now completely out of competition at the Rio Olympics.
Andy Murray makes final 16
Defending tennis champion Andy Murray moved into the third round of the men's singles yesterday. He breezed past Argentina's Juan Monaco 6-3 6-1 – and next faces Italy's Fabio Fognini.
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Team GB kicks off Rugby 7s
The British team kicked off the men's rugby sevens with two victories, beating Kenya 31-7 and Japan 21-19. Japan had earlier pulled off a shock win over joint favourites New Zealand after Kiwi star Sonny Bill Williams was ruled out of the rugby sevens competition through injury.
Simone Biles dazzles in gymnastics
Her impressive vault won America another gold medal, taking their tally up to nine...
And finally... the Olympic diving pool is now green
There's been no official explanation yet, but there's no denying that the pool has changed colour, transforming from crystal clear to a strange, swampy green. More like a pond than a diving pool...
