Under the transparent foil of magnetic sketcher, there are microscopic iron filings floating in a special solution. Moved by the magnetic force of a magnet, the filings attach to the foil. The magnet in the shape of a strip on the other side of the board is used for erasing your doodles.
The screen of the board is divided into hexagonal cells to avoid drawing all the solution in one place. The paraffin oil is the solvent here, and the magnetic material consists of iron file dust or, better, iron oxide. The iron oxide, the magnetic material of the first Chinese compasses (which was discovered in Europe by sailors from the Italian town of Amalfi, South of Naples) is called magnetite.
The magnetic sketcher works on the same principle thanks to which the iron nails or powders orient themselves in the magnetic field. They get magnetised by the external field and follow the magnetic field lines. Such an aligned configuration has a lower energy than separate grains would have.