I'm not saying this is the most dangerous thing I've ever seen on the internet, but it does do a good job of making the Anarchist's Cookbook look like a Health & Safety training manual.
This video is the work of YouTuber/future Darwin Award winner TheBackyardScientist. He demonstrates how to use electricity to burn fractal patterns into wood, creating an undeniably awesome and nerdy thing to hang on your wall.
But this video isn't about the end result — it's how that pattern is burned into the wood. Namely, by hooking up a microwave transformer to mains power, covering the wood with water, and then turning everything on. If you were to accidentally touch that piece of 2000-volt wood, it would be your biggest (and very much final) mistake in life.
Needless to say, you probably shouldn't try this at home — you should sit on the safe side of this computer screen, marvelling from a distance at how this guy is not yet dead, and finding lame posters for your wall instead.