Ferrofluid is a great thing to have around the workbench, especially if you want to quick demonstration to show friends, family, and friends of family, how fun and amazing the fundamental workings of the universe can be to explore. I tried to make home-brew ferrofluid once and failed spectacularly. I couldn't get the procedures I found online to work, and frankly I didn't have time to turn it into a big project. So I was really delighted when Nile Red published his own exploration into the challenge. He apparently had similar results, but, being a relatively well-off YouTuber, he also had to time and the resources to make it work.
So if you'd like to do it, here's the secret!
Enjoy.