Movie S2.

A movie in real time of the breakup during heating of the fiber shown in Fig. 6A of the main text (cross-section shown in Fig. 6B and side view in Fig. 6C). The core consists of a thin glass G1 shell enveloping a PES core containing four parallel G2 filaments. The diameter of this structure is ∼40 μm. Because of their smaller diameter, the four G2 filaments undergo the breakup process first, resulting in four lines of smaller particles. Subsequently, breakup takes place in the outer G1 shell, resulting in large-diameter particles containing the smaller particles aligned along the axis.