An optical lattice is formed by the interference of counter-propagating laser beams, creating a spatially periodic polarization pattern. The resulting periodic potential may trap neutral atoms via the Stark shift. Atoms are cooled and congregate in the locations of potential minima. The resulting arrangement of trapped atoms resembles a crystal lattice. This book presents current research from across the globe in the study of optical lattices, including optical lattices prepared by laser treatment on polymers, peculiarities of magnetooptical properties in crystals with mixed valence centers; the interplay of optical lattices with localized nonlinearity and matter wave dark solitons in optical superlattices..