About the book.... This book is intended for graduate and post graduate students, and researchers planning to start an advanced experimental work in the fast growing field of Liquid Crystals. The scientific world today sees the development and advancement of materials as the key solution to the growing demand for smart devices and innovative technology products finding wide range of applications in optoelectronics. Optical spectroscopy methods have numerous applications in Physics, Chemistry, Material, Biology. The progress in the optical spectroscopy was possible because of great developments in laser physics, optics, electronics and computers. The book has no intention to go deep into its subjects or to provide a complete overview of these broad areas. In turn, it is assumed that readers are already familiar with the subject and the main goal of this part of the book is to remind readers of the key concepts, important theories and principle values and available tools which are used in spectroscopy applications.