Mocha diffusion is a techique for decorating ceramic artwork. Ink mixtrure dripped onto wet clay produces striking branching patterns, similar to those seen in many areas of fluid mechanics. What makes the physics of mocha diffusion unique is the fact that the underlying fluid must be complex. As the wet clay is pushed harder, its viscosity decreases. When combined with surface tension (Marangoni) forces, a the physics of fluids comes alive in the artist's hands.