Ferrocell, an awesome magnetic field viewer, magnetic field perception is undoubtedly better than any other system. It’s easy to make, but be careful, ferrofluid dirt terribly so take precautions to not ruin what’s around.
2 glass sheets or transparent acrylic material
Mineral oil to dilute the ferrofluid
A led strip to highlight the rotation of the ferrocell magnetic particles
Magnets of all shapes and sizes, all you see in the video come from https://www.supermagnete.com
Thanks to Brian Kerr and Ron Blevins for their interesting videos on this subject