Matter contributes about 30% to the energy density of the Universe. Only a sixth of that is ordinary matter that we can identify: you, me, the screen you are looking at, the Earth, the stars, the galaxies, but mostly dust. We know that the rest, about 25% of the Universe, is not of the same kind as you and me (baryons). Direct detection experiments have not produced positive results that point to a new elementary particle that constitutes the dark matter.
Other dark matter candidates are massive compact objects in size comparable to stars. Recently, it was conjectured that primordial black holes could make up the dark matter. Those black holes do not form from stellar remnants. They form very early when the Universe is still extremely hot and dense. The main difference to astronomical black holes is that they there is no lower limit on their mass.
Observational limits on the abundance of primordial black holes allow for them to constitute the dark matter (or conceivably parts of it). My research explores this opportunity with an emphasis on models that lead to a natural production, that does not rely on fine tuning.