You will need:

A shallow bowl or pie dish, food coloring, milk (we used both 1% and half-and-half to compare results; use what you have), a couple of drops of liquid dish soap, and a cotton swab.

Step 1: The Milk

Pour enough milk into the shallow bowl or pie plate to fill the bottom completely. 

Step 2: The Color

Add just a couple of drops of each color of the food coloring. 

Step 3: Dip the Swab

Dip just the tip of the cotton swab into the liquid dish soap.

Step 4: Watch the Color Explosion!

Now dip the tip of the cotton swab into the milk and observe the explosion of color! When liquid dish soap is added to milk with drops of food coloring on the surface, the soap reduces the surface tension of the milk and reacts with the fat. This interaction causes the fat particles in the milk to move and create swirls of color.

Try Different Variations

Try picking up the dish and putting it back down again to observe what happens. Try dipping the cotton swab right into the center of one of the color droplets, or dip the swab into the white spots between the color drops. When the action slows down, dip the other end of the cotton swab into the dish soap and start experimenting again! 

Find this science experiment and more ideas in our 63 Easy Science Experiments for Kids article or peruse our STEM Guide for Kids for more hands-on experiments.