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Martina Hingis at Age 12 at Junior Wimbledon

Chris Cole / Getty Images
Martina Hingis of Switzerland was the most phenomenal of the young female phenoms. Here she is at age 12, playing in the 1993 Wimbledon Junior Girls event shortly after becoming the youngest ever Grand Slam champion by winning the Junior Roland Garros. After her extraordinary junior career, Martina turned pro at the grand old age of 14 and had an outstanding career on the WTA Tour, winning three Australian Opens, one Wimbledon, and one US Open; and finishing 1997, 1999, and 2000 with the world #1 ranking.