  We report on the observation of the polygonal whirlpools in the thin layer of
ferrofluid under illumination with a laser beam carrying optical vortex and in
the presence of a vertical magnetic field. This kind of structures have
attracted attention after discovering a hexagonal storm in Saturns atmosphere.
Our polygonal whirlpools were created in a closed system (no free surfaces) in
micro scale (whirlpool diameter less than 20 micrometers) by the use of
holographic optical tweezers. The polygonal shape was changed by varying the
magnetic field strength or value of the optical vortex topological charge.
