Probing dark matter at small scales and high redshifts

The last decades have firmly established the existence of a dark sector of our universe. Yet, details of its content have evaded all laboratory probes. In this talk I will describe how the cosmic-dawn era, which saw the formation of the first structures, holds a wealth of information about dark matter. We will soon have detailed maps of this era with both 21-cm observatories (like HERA) and space telescopes (such as James Webb). I will show how to use the upcoming data to measure the matter power spectrum at smaller scales—and earlier times—than ever before. This will give us a new handle on the particle nature of dark matter, testing whether it is cold, warm, fuzzy, or self-interacting in a complementary way to local observables.