A man uses an iris recognition scanner during the Biometrics 2004 exhibition and conference October 14, 2004 in London.

The most common biometric security features include fingerprint scanning, facial recognition, voice recognition and iris scanning.

It seems as if every premium smartphone — and even many of the not-so-premium ones — have some form of security feature that uses a body part as a form of authentication.

These features, known as "biometrics," have become a staple on mobile devices, as they serve a number of different functions.

The iPhone 5s was one of the first mainstream devices to feature a fingerprint scanner.

In 2013, when Apple introduced the iPhone 5S, the first major smartphone to feature a fingerprint scanner, it seemed like something out of science fiction.

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