The secret meaning in the Pittsburgh Steelers logo has a particular historical significance.
The Steelers pay tribute to their city's moniker with a logo that honors the American Iron and Steel Institute with its colors.
NFL fans were shocked to discover what each color in the Steelers represented.
Can you guess what they are from looking at the logo?
The three stars in the logo represent materials used in making steel —yellow for coal, orange for iron ore, and blue for steel scrap.
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The Steelmark logo was created to initially represent steel and the steel industry owned by the American Iron and Steel Institute — and was used to promote the product and its manufacturers until the early 1960s.
In 1962, the Steelmark co-owner asked the Steelers owner to place the logo on one side of their helmets, and that decision led them to Pittsburgh's first post-season bid.
The logo started as just "Steel," but after petitioning to change to the team's full name, it was approved and swapped to "Steelers."
The Steelers are the only NFL team to have a logo on just one side of their helmet.
This isn't the only optical illusion in sports, though.
The Arizona Diamondbacks have TWO hidden in their logo - can you see them both?
There's one in the Dallas Mavericks basketball team. Can you see it?
And the one in the Carolina Panthers logo is hard to see - can you guess it?
