My wife is a science teacher, so she has some interesting experiments that she does in her classroom. This one uses whole milk, food coloring, a Q-tip, and some dish soap. In the image below I have some milk in a small container, with drops of different color food coloring arranged around the outside of the container and one drop in the middle. The colors will drift a little like you see here.
Using my Nikon D7000 with the Tamron 90mm macro lens. Tripod Vanguard Altra Pro 263 AT and Acratech Ultimate Ballhead.
Next take a Q-tip and soak the tip in dish soap. Stick the Q-tip end with the dish soap on it into the milk around the edges and swirl it around, and watch the colors go crazy. The dish soap is breaking down the fat in the milk making the colors to move around. That’s why we use dish soap to clean our dishes it breaks up any on the grease and fats on the dishes. So doing the same thing when it comes in contact with the fat in the milk.
Here is what it looks like after applying the soaked Q-tip and moving it around in the milk.
Now try and get your camera over top and parallel to the milk. Shoot at f/8. I also used an LED light on the area.