YouTuber Brainiac75 suffers for science by taking a viewer request to touch the spikes formed by exposing ferrofluid to an extremely powerful neodymium magnet. He also shares some history of the substance.
Ferrofluid is a major skin irritant, so it's best not to replicate this at home. The ferrofluid quickly starts traveling up the ridges of his finger and around his nail. He repeats the touching with a rubber glove on, and the ferrofluid leaves a permanent residue on the fingertip of the glove. It's a little nerve-racking to watch because if he gets the fluid too close to the magnet, the force will be too strong for him to keep it from smashing into the container of ferrofluid.