In the modem world, the development of science & technology in many areas has been achieved through the growth of single crystals. Large sized single crystals are essential for device fabrication and efforts are taken to grow large single crystals in short duration with less cost. Nonlinear optical (NLO) materials are expected to play a major role in photonics including optical information processing, sensor protector applications, data storage ... etc. Some organic compounds exhibit large NLO response, in many cases, orders of magnitude larger than widely known inorganic materials. They also offer the flexibility of molecular design and the promise of virtually an unlimited number of crystalline structures. The present book is aimed towards the development of NLO single crystals of L-Valinium picrate (LVP), L-Histidine hydrochloride monohydrate (LHHM), L-Serine sodium nitrate (LSSN), Bisglycine hydrobromide (BGHB) and Picolinic acid hydrochloride (PHCL) which are all excellent NLO materials are exhibiting NLO property more than that of KDP, and these grown materials can be used as a better replacement for KDP to find applications in the field of opto-electronics.