Millefori by Fabian Oefner
"The shapes, you see in these image are about the size of a thumbnail. They are created by mixing ferrofluid with water color and putting it into a magnetic field.
Ferrofluid is a magnetic solution with a viscosity similar to motor oil. When put under a magnetic field, the iron particles in the solution start to rearrange, forming the black channels and separating the water colors from the ferrofluid. The result are these peculiar looking structures.”