What you need:
- shallow bowl/plate
- 2-3 different colors of food coloring (liquid not gel)
- dish soap
It's cool. We just took a shallow bowl but you can use a plate and poured a little milk in it. I had each boy add a few drops of food coloring, pretty close together in the center of the bowl. Then you add a few drops of dish soap on top of the food coloring and all these cool reactions start happening in the milk.
The boys were very happy and wanted to do it again and again and again....