The nature of dark matter is unknown. A number of dark matter candidates are quantum flavor-mixed particles but this property has never been accounted for in cosmology. In this talk, we first discuss an interesting and rather counter-intuitive property of non-relativistic flavor-mixed particles called “quantum evaporation” — a quantum effect, which is not related to flavor oscillations, particle decay, tunneling or other well-known processes. Particularly, we will show that a mixed particle confined in a gravitational potential and scattering off other particles from time to time, can gradually and irreversibly escape from it without extra energy supply. Furthermore, we discuss how this effect alters the structure formation in cosmology with multi-component mixed dark matter. We demonstrate, from the first principles via extensive N-body cosmological simulations, that such a dark matter model agrees with observational data at all scales, in contrast to the conventional LambdaCDM. Substantial reduction of substructure and flattening of density profiles in the centers of dark matter halos found in simulations can simultaneously resolve several outstanding puzzles of modern cosmology. Finally, we discuss the predictions of the model for direct and indirect detection dark matter experiments.