@scroll.engineer: Your Samsung phone is secretly using sound to read your fingerprint. 🤯 Most people think the fingerprint sensor is just taking a picture of their finger. But on many Samsung Galaxy phones, something much more interesting is happening beneath the screen. When you touch the display, an ultrasonic sensor sends tiny sound waves into your fingertip. Those waves bounce back differently depending on the microscopic ridges and valleys of your fingerprint. Your phone uses those returning echoes to build a detailed 3D representation of your fingerprint and compare it against your stored biometric data. And because it uses sound instead of light, it can work even in complete darkness. All of that happens in a fraction of a second, just to unlock your phone. Did you know your phone was doing all of this every time you touched the screen?