Regular self-similar pattern when ink dissolves in water

This is a demo of phenomenon that showed by J. J. Thomson more than one hundred years ago in “On the Formation of Vortex Rings by Drops Falling into Liquids, and Some Allied Phenomena“. It was a big surprise to me when I saw it. A recent interesting paper on Nature Physics called “Single-drop fragmentation determines size distribution of raindrops“ that shows an amazing aspect of similar phenomenon but in the case of raindrop.