In order to have the ability to control a liquid inside a container, say an engine, in space, NASA engineered ferrofluid. Otherwise, a standard liquid inside a container without the pull of gravity to hold it in would not stay at the bottom of the container but would float to the sides and top. Ferrofluid is attracted by magnetic forces so gravity does not have to be present to control it.
By exposing the ferrofluid to a strong magnet, the fluid creates liquid spikes in response to the magnetic field. The liquid spikes appear solid, but on an experimental touch, they move as a liquid. In addition to ordinary spikes, if the magnet is close enough and strong enough, it can cause the ferrofluid to build tiny needles upon the spikes. The spikes are formed following magnetic field lines coming from the magnet. Because the ferrofluid is a liquid, surface tension helps to create uniform spikes.
(Video: Brainiac75)