Introduction
Liquid droplets are naturally driven into a spherical shape by surface tension. That is why non spherical droplets rarely exist in nature. Our goal is to generate such rare droplets and study their hydrodynamic behavior as a function of geometrical parameters.

Observations
Newtonian toroidal droplets in another Newtonian medium are unstable and always transform into spherical droplets. There are two different paths of transformation depending on the aspect ratio of the torus.

For a thin torus, where the curvature associated to the overall size of the torus is insignificant compared that associated to the tube radius, the Rayleigh-Plateau Instability induces the transformation of the toroidal droplet into spherical droplets, similar to what happens for cylindrical jets. However, unlike for cylindrical jets, only integer values of the perturbation wavelength can fit inside the torus. As a result, by controlling the aspect ratio of the torus and the viscosity ratio between two liquid interfaces, the droplet breaks in a precise number of spherical droplets.

    
Figure 1: Viewing from the bottom of breaking Torus (left) and Viewing from the side of breaking Torus (right).