Through weak lensing and galaxy clustering measurements, the next generation of large-scale surveys (Euclid, LSST, ...) will provide unprecedented observations and constraints on the late Universe, and thus shed light on dark matter and dark energy. On the other hand, high-quality CMB observations (current and planned) can -- and already do -- put tight constraints on the early Universe and its content.

Primordial black holes can form in the early Universe from the collapse of cosmological perturbations after the cosmological horizon crossing. They are possible candidates for the dark matter as well as for the seeds of supermassive black holes observed today in the centre of galaxies. In calculations of spherically symmetric collapse, a Lagrangian relativistic hydrodynamical code is used to follow the non linear evolution. If the perturbation is larger than a threshold depending on the equation of state and on the specific shape of the perturbation, a black hole is formed.

Cosmic strings (CS) are topological defects formed after spontaneous breaking of a U(1) symmetry. Remarkably, thanks to the scaling regime, CS loops constitute a long-standing source of Gravitational Waves (GW) and produce a flat GW spectrum during radiation domination, spanning many orders of magnitude in frequency.