The dots are invisible to your eyes. But you can see them through an infrared camera. The iPhone X's camera analyzes the dots on your face and compares it to the image made when Face ID was set up.

Recently, iPhone users have become afraid that the front facing camera might be taking photos of them every five seconds. As ...

The infrared cameras can detect hidden water leaks or ... This one works with Android smartphones. If you have an iPhone, you’ll want the TI222. I have a collection of infrared images taken ...