The current status and prospects are examined of the rapidly developing field that studies the structure and properties of lyotropic nematic liquid crystals. Typical amphiphiles are presented, and systems based on them. Typical textures and their optical properties are examined. The physical properties of nematics are described in detail: diamagnetic, dielectric, and viscoelastic. A special section is devoted to biaxial nematics, which have no analogs among the thermotropic nematic liquid crystals. The features of their order parameter and elastic properties are examined. Textures and optical properties are described. Further, molecular ordering (from NMR data) and features of phase transitions are discussed. In closing, lyotropic cholesterics are discussed, both those based on individual chemical compounds and those induced by chiral additives.