The book presents technologically important four organic NLO crystals particularly, HA, 2A-5CB, LAA and LTN.It explains the various methods of crystal growth in detail. A literature survey on various NLO crystals is provided with references. Also explains the various tools and techniques for characterizing the crystals. The optimized growth conditions and physico chemical properties of pure and Acetanilide, Benzamide and Urea doped Hippuric Acid (HA), pure and Benzophenone, Benzoic acid and Paratoluidine doped 2-Amino-5-Chloro Benzophenone (2A-5CB), pure and Cu2+ and Mg2+ doped L-Arginine Acetate (LAA) and pure and Cu2+ and Zn2+ doped L-Tartaric Acid Nicotinamide (LTN) NLO single crystals. The variation of growth parameters and physico chemical properties of these crystals were compared and reported in detail.