Ferrofluid in a bottle and supplied with a magnet. Ferrofluid is a black runny fluid.... that reacts to magnetic fields, often changing into seemingly impossible shapes as it tries to maintain the shape of the magnetic field. This gas bottle has ferrofluid which is suspended in a clear fuild allowing you play with the ferrofluid without ever getting messy ! It is mesmerising and strangely very enjoyable to manipulateblack liquid at will. Comes in a a fairly tall glass bottle(about 34mm wide, 120mm tall, 34mm deep). Please make sure you keep at room temperature to avoid cracking of the glass.