What is Ferrofluid? In short, it is a liquid that responds to magnets and magnetic fields. Ferrofluid is an extremely fine powder, coated with a soap-like material called a surfactant, and suspended in a mineral oil liquid base. The resulting magnetic suspension is called a ferrofluid. When no magnetic field is present, ferrofluid behaves and flows like a normal liquid. However, when a magnet or magnetic field is introduced, the ferrofluid is attracted to the field. The ferrofluid aligning itself to the magnetic fields creates fun and interesting shapes and lines, letting you see what a magnetic field looks like.