The objective of this book will be to explore the possible applications in the field of spectroscopy toward matters related to security, the environment and forensics, with in-depth analyses of relative difficulties and advantages of the various techniques. Spectroscopic techniques have been contributing significantly to diverse areas, such as material processing and characterisation, communication, forensic science, and defence with an unequalled precision by using lasers. Raman and infrared spectroscopic techniques are regularly used in the studies on semiconductors, microelectronics, catalysis and nano-materials. With the advent of nanotechnology, new materials are being reported with an improved sensitivity to various toxic gases, finger printing etc. Photo acoustic spectroscopy, with a quartz tuning fork sensor, makes it possible to detect trace amounts of explosive powders and residues on surfaces from a distance. Laser induced breakdown spectroscopy from the Curiosity rover, roaming the Mars surface, has been sending valuable spectral data that will be used to understand the existence of life. The present book encompasses a wide range of topics pertaining to the variety of spectroscopic techniques which would be of great importance in the detection of explosives, chemical and biological agents and in meeting any defence threats.