You may want to think twice before taking part in the popular "10 Year Challenge" on social media.

The challenge involves showing off side-by-side pictures of yourself -- one from 10 years ago and another from now.

But now the questions being raised are: Who's behind the meme? And could the photos, with specific date tags, be used by computers for facial recognition training without you knowing?

Technology and social media expert Lance Ulanoff says the 10-year posting trend should serve as a reminder about what kind of data is shared on social media or through things like quizzes that ask for all sorts of information, personal or otherwise.

"You are literally handing Facebook data as we do every single day," Ulanoff says. "It's a question of what is Facebook gonna do with that data."

For its part, Facebook said in a tweet that it's not behind the challenge and that its servers are not tracking the photos.

Bottom line, Ulanoff says think twice before sharing information or pictures on social media especially if it could be public.

Anthony Franzini, of Mineola, says he's careful about what he posts on social media, while East Meadow's Amanda Accetta says it's fun to see how people change within a decade.