Pour a bit of milk on a shallow plate.
Put in a few drops of food coloring at the sides.
Dip a cotton bud in dish washing soap and then dip it in the middle of the milk mixture. Watch magic happen!
I’ve been told that this is used for adult psychotherapy and read that they use this experiment for bigger kids to discuss molecules.
My toddler enjoyed “making orange and black” with the swirling, whirling colors.