Abstract
The Big Bang theory describes an expanding Universe, in which large structures are formed by gravitational collapse. These are the galaxies, filaments, walls and cosmic voids that surround us. The embryos of these structures are the quantum fluctuations of the vacuum, shaped during a phase of accelerated expansion known as inflation . This radical hypothesis, which assumes that every structured element (galaxy, star, planet, human being, etc.) proceeds from quantum fluctuations in the primordial Universe, has been remarkably confirmed by measurements of the cosmic microwave background, the fossil light that the Universe let out in its earliest instants. The possibility that some of these anomalously large fluctuations could collapse into " primordial black holes " has recently received increasing attention, as these black holes could constitute the dark matter of the Universe. We will return to these key elements of primordial cosmology, and highlight some of the open questions that constitute avenues of research to be explored.
