WATCH: How Stan Smith became a fashion icon

CNN’s Open Court takes a look at how two-time Grand Slam champion Stan Smith became more famous for his shoes than his tennis success. The American won the US Open 1971 and Wimbledon in 1972, prompting Adidas to put his name and face on their tennis shoe in 1972.

Adidas has sold more than 40 million pairs of the white leather Stan Smith sneaker, and released an updated version in 2014.

"It was the most high tech shoe when it came out in 1965," Smith said. But he doesn't recommend competing in it anymore.

"Some people said to me, you know about 95 percent of people in the world have no idea who you are… as a person," Smith said "But they know the name because of the shoe."

He admits he sometimes asks people he spots wearing the sneaker if they know who Stan Smith is, and they don't usually know.

These days, the former No. 1 is becoming more well-known as something completely unexpected, a fashion icon