This simulation shows hydrodynamic instability triggered by rapid cooling in a heavy-element-enriched cosmic dark matter halo when the universe was only 300 million years old. The instability drives turbulence which breaks the flow into fragments. Some fragments undergo gravitational collapse and set to fragment into progressively smaller units. From left to right and top to bottom, the six panels show projections of gas density, and the horizontal bar has length 1 pc = 3.26 light years.