Why Do Mirrors Work the Way They Do Work?

Why do mirrors flip left and right and not up and down? Have you ever thought about it? 

Mirrors are one of the mysteries in the world, maybe not at the moment but I'm sure they were a mystery when they were invented for the first time in history. 

Now, mirrors are easy for scientists to explain, there's even a field of it in physics. But it can still be difficult for some of you out there to understand why it works the way it does. For example, why does it flip left and right, but not up and down, as I wrote before? 

It's not that complicated to understand actually. This video explains clearly why it does work like that, and I'm sure you won't have any other questions in mind after watching the video. 

So go ahead and watch the video to figure out one of the biggest(!) mysteries of the world.