Fingerprint technology at heart of iPhone 5S

It was the most buzzed-about rumor ahead of the iPhone 5S's launch, and the fingerprint scanner was the most discussed new feature on the phone after Tuesday's presentation.

The scanner -- called Touch ID -- is a sensor embedded in the iPhone's home button, is first and foremost a security function. But fingerprint recognition will also have functionality throughout the phone's apps.

The sensor, made from a laser-cut sapphire crystal, replaces the home button. It is surrounded by a stainless steel detector ring, which wakes up the sensor when its activated. The crystal directs the image to the capacitive touch sensor, which reads underneath the outer layers of the skin to get an accurate, detailed print that is analyzed by software to identify a match.

Apple touted the sensor as extremely capable: Not only can it recognize a finger print from any angle, so its not necessary to carefully align your finger to the device, but it can learn multiple prints, so users can share their "password" with those they trust.

The tech company also made sure to point out a user's fingerprint data will be stored on the phone's A7 processor chip-powered internal architecture, not anywhere on Apple's servers, and ostensibly, out of reach of any snooping.

And once the phone is unlocked, the new iOS will allow fingerprints in place of passwords for purchases made in the App Store, iBooks Store and iTunes.

The iPhone 5S will ship September 20, at $199 for a 16GB phone, $299 for a 32GB, and $399 for a 64GB device, all on contract.