Great question! You see finger print scanners on lots of devices these days – including mobile phones.
Secret codes are a great way to keep things private and safe, as you’ll know if you have a combination lock on your diary or bike!
Human beings are lucky because every single person alive has their own, totally unique secret code – on their fingers and thumbs!
On each finger pad, you can see a pattern of swirls and ridges. Yours won’t match anyone else’s. The first time you set the lock, you let the scanner take a picture of your fingertip.
Every time you then swipe your fingertip on the reader, it takes another photo and checks the first to see if they match. If they do, you’re in!
Sometimes electrical currents are used instead of light.
You might know that electricity is carried around gadgets and machines in channels called circuits. They’re like roads – if there’s a gap in the circuit the electricity can’t flow, just like cars can’t cross a broken bridge.
Some scanners use circuits which are completed or filled by the bumps of the fingerprint. The pressure activates switches which help the device put together an image of all the ridges and can compare them to its original.