  In this report we summarize a recent progress in exploration of correlated
two-dimensional electron states in partially filled high Landau levels. At a
mean-field Hartree-Fock level they can be described as charge-density waves,
either unidirectional (stripes) or with the symmetry of the triangular lattice
(bubbles). Thermal and quantum fluctuations have a profound effect on the
stripe density wave and give rise to novel phases, which are quite similar to
smectic and nematic liquid crystals. We discuss the effective theories for
these phases, their collective modes, and phase transitions between them.
