Smile! ‘Cause we can all see you.

Once the stuff of science fiction, facial recognition technology is increasingly creeping into our everyday lives. Facebook and Google use it for auto-tagging photos. Snapchat uses it to create silly filters. And Apple’s new iPhone X lets users actually unlock their phones with their faces.

But, as the latest Above the Noise video explains, the technology is also being used by governments and companies in an effort to learn as much about you as possible. In the U.S., there are an estimated 60 million surveillance cameras, which means there’s a pretty good chance that our faces are being digitally captured every time we step outside.

In many U.S. airports, facial scans are regularly checked against photos stored in police databases. In fact, if you’re an adult in the U.S., there's a 50 percent chance your photo is stored in a police database somewhere, even if you’ve never been arrested or charged with a crime.

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As Jennifer Tucker, a history professor at Wesleyan University, wrote in a 2014 Boston Globe article:

“There’s something unsettling about the notion that the government is actively trying to recognize its citizens by face: It suggests that the simple liberty of going out in public anonymously could become a thing of the past.”

Facial recognition has repeatedly come under fire from privacy advocates who worry it gives the government -- and increasingly, private companies -- access to reams of personal information without offering any chance to opt out.

In a 2012 U.S. Senate hearing on the emerging technology, an attorney for the Electronic Frontier Foundation, an online privacy group, testified that “Americans cannot participate in society without exposing their faces to public view.” And even Eric Schmidt, executive chairman of Google (a key player in the development of commercial-use facial recognition technologies), admitted that he finds the technology somewhat “creepy.”

But facial recognition, Tucker notes, is just the latest chapter in a nearly 200-year history of law enforcement agencies trying to identify and generally keep track of real and perceived wrongdoers.

Most emerging identification technologies, she said, were also considered invasive, prompting similar privacy concerns. But ultimately, most of those technologies were accepted as necessary tools for security.

“The belief that crime can be defeated through technological means propels innovations in the field ever onward,” she said.

Scroll through this interactive timeline of various law enforcement-related identification technologies, once considered cutting edge and controversial, that have emerged since the mid-1800s.

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Profiled: A Brief History of Identification (Interactive Timeline and Lesson Plan)