Photos: A look at Serena Williams' 21 Grand Slam singles titles

2002 French Open (Michel Euler / AP)

2002 Wimbledon (Dave Caulkin / AP)

2002 U.S. Open (Tim Clary / AFP)

2003 Australian Open (Steve Holland / AP)

2003 Wimbledon (Odd Andersen / AFP/Getty Images)

2005 Australian Open (Steve Holland / AP)

2007 Australian Open (Clive Brunskill / Getty Images)

2008 U.S. Open (John G. Mabanglo / EPA)

2009 Wimbledon (Peter van den Berg / AP)

2010 Australian Open (Julian Abram Wainwright / EPA)

LONDON, ENGLAND - FILE: Serena Williams of USA celebrates a point during the Ladies Singles Final Match against Vera Zvonareva of Russia on Day Twelve of the Wimbledon Lawn Tennis Championships at the All England Lawn Tennis and Croquet Club on July 3, 2010 in London, England. It was reported that tennis star Serena Williams is recovering in a Los Angeles’ Cedars Sinai Medical Center after undergoing emergency treatment on February 28 for a blood clot in her lungs March 2, 2011. (Photo by Julian Finney/Getty Images) (Julian Finney / Getty Images)

2009 Australian Open (Oliver Weiken / EPA)

2012 Wimbledon (Julian Finney / Getty Images)

2012 U.S. Open (Mike Groll / AP)

2013 French Open (Caroline Blumberg / EPA)

FILE - In this Sept. 8, 2013, file photo, Serena Williams hugs the championship trophy after defeating Victoria Azarenka, of Belarus, in the women’s singles final at the U.S. Open tennis tournament in New York. Williams earned her 17th major title at the U.S. Open this month. Tennis great Steffi Graf, who won 22 titles, believes Williams will surpass Margaret Court’s record of 24 Grand Slam singles titles. (AP Photo/David Goldman, File) ** Usable by LA and DC Only ** (David Goldman / AP)