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A strongly chiral liquid-crystal phase containing local double-twist order and frustrated regions. Ordered blue phases I and II have body-centered cubic and simple-cubic director/defect structures respectively, while blue phase III is disordered. The periodicity is orientational/defect order, not a molecular positional crystal lattice.

The blue phases result when strong local chirality favors double twist that cannot fill three-dimensional space everywhere without frustration. Double-twist regions are connected through a network of nematic disclinations.

Blue phase I has body-centered cubic order and blue phase II simple-cubic order in their director/defect structures. The periodicity can cause selective optical reflection. Blue phase III is disordered or amorphous, not another ideal cubic lattice. These are structured fluid phases rather than ordinary crystals with molecules fixed to every lattice site.