Sometimes we take for granted the fact that we drive around the planet in little boxes of glass. But there's actually some really cool physics that goes into making car windows, and Destin from Smarter Every Day is here to explain it, with one of the coolest slow-motion demonstrations we've seen in a long time. And it could save your life one day.

To start with, you need to know that there are two types of glass in your car – annealed glass in the windscreen and tempered glass in the windows.

These are specially designed to keep you safe during a crash (and prevent your windscreen from breaking and slicing you in half) but they also do some cool things when you hit them with a hammer.

We don't want to give too much away because you should really watch the video above – in all its 20,000 frame per second glory – but we will say that tempered glass does some pretty crazy stuff if you can manage to release the tension inside. It's kind of like a Prince Rupert's Drop, but flat.

Check out the video above, and then watch Destin showing just how cool a Prince Rupert's Drop is in slow motion.