The IDEMIX concept is an energetically consistent framework to describe wave effects in ocean circulation models. It is based on the radiative transfer equation for a gravity wave field in physical and wavenumber space. For IDEMIX the radiative transfer equation is integrated in the wavenumber and frequency domain, leading to conservation equations for integral energy compartments in physical space. These equations can be closed with a few simple but reasonable parameterizations. IDEMIX describes the generation, interaction, propagation and dissipation of the internal gravity wave field and can be used in ocean general circulation models to account for vertical mixing and wave drag in the interior of the ocean. We review the physical ingredients of the current IDEMIX versions and demonstrate their performance for ocean applications.