While most rare earth magnets are made from the rock hard materials we’re familiar with, not all appear in that classic solid form. Ferrofluid is a stable colloidal suspension of superparamagnetic iron oxide nanoparticles. So, simply, it is a liquid that contains tiny magnetic particles. It’s magnetic properties comes from the magnetized iron oxide it contains. These particles are known as nanoparticles because of their small size -- the particles are actually so small that they never fully settle to the bottom of their container!