Spectroscopy is the study of the interaction of electromagnetic radiation in all its forms with the matter. The interaction might give rise to electronic excitations, (e.g. UV), molecular vibrations (e.g. IR) or nuclear spin orientations (e.g. NMR). Thus Spectroscopy is the science of the interaction of energy, in the form of electromagnetic radiation (EMR), acoustic waves, or particle beams, with the matter. Here in this article, the matter is studied in further detail.