Is it a robo-hedgehog? A Lady Gaga headpiece? Or merely a new way to juice lemons? No. In fact, it’s not even a solid object: it’s a ferrofluid.
Ferrofluids are colloidal mixtures – where one substance is microscopically dispersed evenly throughout a carrier fluid – containing magnetic nanoparticles. When placed in a magnetic field, the suspended particles cause the entire fluid to become strongly magnetised.
In this image a small drop of ferrofluid is placed within a magnetic field created by a neodymium iron-boron rare-earth magnet. The peaks and troughs result as the magnet tries to pull the liquid along its field lines.