The process shown in the video above makes use of a phase field model to track the evolution of the interface between a supercooled liquid and a solid. While this seemed like unfamiliar territory at first, a quick look under the hood revealed a set of reaction-diffusion-like equations. The system is represented by two co-dependent scalar fields – one representing temperature and one representing the phase. The latter is either 0 (liquid) or 1 (solid) everywhere in the system except at the interface where it grades smoothly between the two extremes. At each step, the current temperature contributes to the change in phase and the change in phase contributes to the change in temperature. Over time, this feedback leads to instabilities in the interface which result in all the fancy branching patterns.