The teams who have dominated the doubles game and risen to the top of the WTA rankings together.
Lisa Raymond and Rennae Stubbs were the best doubles team at the start of the new millenium; the US-Aussie pair began 2000 with their first major title at the Australian Open, becoming Co-No.1s just before that year's US Open.
Virginia Ruano Pascual and Paola Suárez became Co-No.1s in the summer of 2004 after capturing the first two legs of the Calendar Year Grand Slam, winning a total of eight majors as a team.
Lisa Raymond ascended to Co-No.1 again in 2006, this time with Aussie Sam Stosur, with whom she reached five major finals - winning two at the 2005 US Open and 2006 French Open.
Liezel Huber joined Cara Black atop the WTA Doubles rankings at the end of 2007, when the team won the WTA Finals in Madrid - capping a successful successful season that saw them win two of the four major tournaments at the Australian Open and Wimbledon.
The sport's preeminent sister act, Venus and Serena Williams have dominated the doubles scene throughout their storied singles careers, winning three Olympic Gold medals in addition to their 13 Grand Slam doubles titles.
Flavia Pennetta joined partner and good friend Gisela Dulko a few weeks after the two won their first Grand Slam title at the Australian Open; the team known as Dulketta had also ended 2010 with a win at the WTA Finals in Doha.
Katarina Srebotnik and Kveta Peschke both became No.1 for the first time after winning their first major title at the 2011 Wimbledon Championships.
Liezel Huber become Co-No.1 with a second partner in the spring of 2012; that partner was none other than Lisa Raymond, who was back at Co-No.1 with a third partner in her historic career. The Americans paired up ahead of the London Olympics.
Italians Sara Errani and Roberta Vinci had each been No.1 apart, but finally shared the top spot in 2013, not long after toppling the Williams sisters en route to their first Australian Open title.
Hsieh Su-Wei and Peng Shuai had burst onto the scene in 2013 after winning the Wimbledon Championships.
Sania Mirza capped an undefeated run through three straight tournaments by reaching No.1 last spring, but it wasn't until the start of 2016 that Swiss Miss Martina Hingis was able to ascend to the top spot as well.
Latisha Chan and Martina Hingis topped the rankings in 2017 (Getty)
Ekaterina Makarova and Elena Vesnina, pictured in Madrid, assume the summit after Roland Garros 2018 (Getty)