In this talk I will first review the standard mechanisms for thermal relic production from the early universe, i.e. freeze out and freeze in. In the first case a species leaves thermal equilibrium at some point in the thermal history, while in the second it never attains it due to a very small coupling with the thermal bath. I will then consider a DM model with a new sector comprising of a Dark Matter fermion and a colored, heavier scalar, Yukawa-coupled to a Standard Model quark. In this model the DM fermion is produced both from freeze in and from the later decays of the frozen-out scalars. I will discuss how thermal effects such as the emergence of collectivity, of screening and of multiple interactions can be accounted for. I will show how they can significantly alter the standard expectation, namely that freeze-in production is dominated by temperatures of the order of the mass of the DM particle.
