The Nature of Low-Density Star Formation

How do stars manage to form within low-density, HI-dominated gas? Such environments provide a laboratory for studying star formation with physical conditions distinct from starbursts and the metal-rich disks of spiral galaxies where most effort has been invested. Here we outline fundamental open questions about the nature of star formation at low-density. We describe the wide-field, high-resolution UV-optical-IR-radio observations of stars, star clusters and gas clouds in nearby galaxies needed in the 2020's to provide definitive answers, essential for development of a complete theory of star formation.