This is so unbelieveable, I had to watch it twice. Needless to say, cornstarch water behaves very strangely when shaken (but not stirred) by high-speed vibrations. The result are faraday waves.
Faraday waves are nonlinear standing waves that appear on liquids enclosed by a vibrating receptacle. They are named after Michael Faraday, who first described them in an appendix to an article in the Philosophical Transactions of the Royal Society of London in 1831.
If a layer of liquid is placed on top of a vertically oscillating piston, a pattern of standing waves appears which oscillates at half the driving frequency. These waves can take the form of stripes, close-packed hexagons, or even squares or quasicrystalline patterns.
The phenomenon has been described and published in 2004 by a group at the University of Texas, Austin.