This is what happens when you mix ferrofluid and watercolours to make art
ferrofluid
Image: Fabian Oefner

Ferrofluid is a liquid made out of tiny particles of magnetite, hematite or some other compound containing iron suspended in an oil-based substance. It was invented in 1963 by Steve Papel, a scientist at NASA who was trying to develop a liquid fuel that could be drawn towards a pump in a weightless environment using a magnetic field.
 
When ferrofluids are exposed to a magnet, they seem to come alive. Photographer Fabian Oefner, who loves to combine art and science, decided to take advantage of this effect and added watercolours (or aquarelles) to ferrofluid. The outcome is fascinating:

“If watercolours are added to the ferrofluid, the pop-art looking structures start to appear, forming black channels and tiny ponds filled with rainbow-coloured surfaces. The reason why the black ferrofluid and the watercolours don’t mix is that ferrofluid is, just like oil, hydrophobic. It therefore doesn’t mix with the watercolours. At the same time it is held in position by the magnet underneath it. So it tries to find a way around the watercolours and therefore forms these black channels,” explained Oefner at Minimo Graph.
 
Oefner named the project Millefiori (a thousand flowers). The shapes are about the size of a thumbnail.
 
Pretty amazing, huh?

Source: Minimo Graph