Phelps' 20 medals -- and counting

Aug. 2, 2012: United States' Michael Phelps leads compatriot Ryan Lochte during the men's 200-meter individual medley swimming final at the Aquatics Centre in the Olympic Park during the 2012 Summer Olympics in London. Phelps earned his 20th Olympic medal in this race. (AP)

July 31, 2012: From left, United States' Michael Phelps, United States' Conor Dwyer, United States' Ricky Berens and United States' Ryan Lochte pose with their gold medals for the men's 4x200-meter freestyle relay swimming final at the Aquatics Centre in the Olympic Park during the 2012 Summer Olympics in London. (AP)

July 31, 2012: United States' Michael Phelps waves after receiving his silver medal in the men's 200-meter butterfly swimming final at the Aquatics Centre in the Olympic Park during the 2012 Summer Olympics in London. (AP)

July 29m 2012: From left, United States' Cullen Jones, United States' Ryan Lochte, United States' Nathan Adrian and United States' Michael Phelps pose with their silver medals for the men's 4x100-meter freestyle relay final at the Aquatics Centre in the Olympic Park during the 2012 Summer Olympics in London. (AP)

Aug. 12, 2008: Michael Phelps of the U.S. celebrates with his gold medal after winning the men's 200m freestyle final at the National Aquatics Center during the Beijing 2008 Olympic Games. (Reuters)

Aug. 16, 2008: Michael Phelps of the U.S. celebrates after winning the men's 100m butterfly swimming final at the National Aquatics Center during the Beijing 2008 Olympic Games. (REUTERS)

Aug. 13, 2008: Michael Phelps, Ryan Lochte, Ricky Berens and Peter Vanderkaay of the U.S. listen to the national anthem during the medal presentation ceremony after the men's 4 x 200 meters freestyle relay swimming final at the Beijing 2008 Olympic Games. (Reuters)

Aug. 15, 2008: Gold medallist Michael Phelps (C) of the U.S., silver medallist Laszlo Cseh (L) of Hungary and bronze medallist Ryan Lochte of the U.S. pose after the medal presentation ceremony for the men's 200m individual medley swimming final at the National Aquatics Center during the Beijing 2008 Olympic Games. (Reuters)

Aug. 13, 2008: Gold medalist Michael Phelps of the U.S. stands with silver medalist Laszlo Cseh (L) of Hungary and bronze medalist Takeshi Matsuda (R) of Japan after the men's 200 meters butterfly final during the Beijing 2008 Olympic Games at the National Aquatics Centre. (Reuters)

Aug. 10, 2008: U.S. President George W. Bush (L) and his father former President George H. W. Bush (2nd R) pose for a photo with the Beijing 2008 Olympic men's 400m individual medley gold medalist Michael Phelps (R), and men's 400m freestyle bronze medalist Larsen Jensen (2nd L) at the National Aquatics Center in Beijing. (Reuters)

Aug. 11, 2008: Cullen Jones, Jason Lezak, Michael Phelps and Garrett Weber-Gale of the U.S. hold up the U.S. flag as they celebrate with their gold medals after winning the men's 4x100m freestyle relay swimming final at the National Aquatics Center during the Beijing 2008 Olympic Games. (Reuters)

Aug. 17, 2008: Michael Phelps of the U.S. receives his gold medal for the men's 4x100m medley relay swimming final during the 2008 Beijing Olympics. Phelps won his eighth gold medal of the games in the race. (Reuters)

Aug. 16, 2004: Michael Phelps of the U.S looks at the scoreboard after the men's 200 metres freestyle final at the Athens 2004 Olympic Games. Australia's Ian Thorpe get the gold medal while Phelps took the bronze. (Reuters)

Aug. 15, 2004: Neil Walker, Jason Lezak and Michael Phelps of the U.S. leave the pool deck while South Africa's team poses for photographers after the men's 4x100 metres freestyle relay final at the Athens 2004 Olympic Games August 15, 2004. South Africa took the gold medal in a time of 3 minutes 13.17 seconds. (Reuters)

Aug. 17, 2004: Michael Phelps (L) and Ryan Lochte (R) of the U.S. celebrate their gold medal in the men's 4 x 200 freestyle relay at the Athens 2004 Olympic Games. (Reuters)

Aug. 2004: Michael Phelps holds up his gold medal after winning the 200-meter butterfly at the Athens Olympics. (Reuters)

Aug. 20, 2004: Michael Phelps of the U.S. celebrates his gold medal at men's 100 metres butterfly final at the Athens 2004 Olympic Summer Games, collecting his fifth gold medal of the Games. (Reuters)

Aug. 19, 2004: Michael Phelps of the U.S. smiles while holding his gold medal he won in the men's 200 individual medley at the Athens 2004 Olympic Games. (Reuters)

Aug. 14, 2004: Michael Phelps of the U.S. swims during the men's 400 metres individual medley final at the Athens 2004 Olympic Summer Games. Phelps set a world record time of four minutes 08.26 seconds to win the gold. (Reuters)

Aug. 21, 2004: Michael Phelps, of the United States, congratulates compatriot Ian Crocker after Crocker won a gold medal as part of the 4 x 100-meter medley relay at the Olympic Aquatic Centre during the 2004 Olympic Games in Athens. Phelps gave up his spot in the final to Crocker, but will still earn a gold medal for for swimming in the preliminaries, giving him six golds and two bronzes. (AP2004)