Streaming Instability: Born Again

The ‘streaming instability’ (SI) between dust and gas in protoplanetary disks is the leading mechanism to form planetesimals — the building blocks of planets. However, the simplicity of the SI is challenged by the complex physics involved in a realistic protoplanetary disk. I describe how turbulence, disk structure, and thermodynamics can hinder the SI; but also how accretion flows and magnetic fields can revive it in modified forms, which injects new hope into planet formation.