The Standard Model of particle physics needs to be completed to address observational facts such as the matter antimatter asymmetry and the dark matter of the universe, as well as the origin of inflation. These, together with a number of other fundamental theoretical puzzles associated with e.g. the flavour structure of the matter sector and the ultra-violet properties of the Higgs scalar field, motivate extensions of the Standard Model featuring new degrees of freedom and new energy scales. In turn, such new physics can substantially impact the expansion history in the early universe and leads to deviations with respect to the standard cosmological model. Any deviations in the Friedmann equation occurring at temperatures above the MeV remain to date essentially unconstrained.