This image provides an interesting perspective on the fluid mechanics behind mixing creamer into coffee. The difference in fluid density leads to a Raleigh-Taylor Instability. Pouring the creamer into the coffee from above also yields a difference in velocity between the two fluids, which causes a Kelvin-Helmholtz instability. Both of these instabilities are responsible from driving the interaction between the two fluids.
Full report can be found here: https://www.flowvis.org/wp-content/uploads/2020/12/IV1-Report-DK.pdf