This is a particularly safe and simple experiment that can be carried out at home with no risk and minimal setup. It’s performed here by a lovely autistic chap by the name of “Doctor Mad Science” whose passion is quite contagious.
What causes the dye to move to the edges of the bowl, you ask? Just like water, milk holds tension well, which is why the dye dropped in the milk moves very little initially. The addition of soap to the centre of the bowl breaks the surface tension and sends the dye hurtling outwards, where tension is still pulling away.