Movie S1

Rayleigh–Plateau instability of a torus, observed from above, with an initial aspect ratio ξ≈3.5. The inner liquid is a solution of 0.1 wt% PEG 8,000 in water, and the outer liquid is a 60,000 cSt silicone oil. Due to the large viscosity contrast between the outer and inner liquids the torus breaks at a single point. The evolution is in real time.