The couple Marlene Heyman (L) and Lucia Christe warm up at the Tango World Tournament in Buenos Aires on August 20, 2013

The couple Marlene Heyman (L) and Lucia Christe warm up before competing during the qualification round of the Tango World Tournament in Buenos Aires on August 20, 2013. The sexy, sensual world of tango is experiencing a shake-up, as same-sex couples compete for the first time in the world championships in Argentina, where the dance was born.