Circular conversion dichroism with almost ideal efficiency has been achieved in metamaterial-based chiral mirrors. In contrast to conventional mirrors, a chiral mirror reflects circularly polarized waves of one handedness without handedness change, while absorbing circularly polarized waves of the other handedness. Chiral mirrors can be realized by placing a 2d-chiral metamaterial in front of a conventional mirror. The concept has been exploited in holography to realize independent holograms for left-handed and right-handed circularly polarized electromagnetic waves. Active chiral mirrors that can be switched between left and right, or chiral mirror and conventional mirror, have been reported.