This chapter explores the fundamentals and uses of spectroscopy, with an emphasis on optical techniques such as UV-visible, near-infrared (NIR), and Fourier-transform infrared (FTIR) spectroscopy. The chapter begins with an overview of the theoretical foundations of each spectroscopic technique, detailing their operational principles and the types of interactions between light and matter they exploit. It then explores the instrumentation and methodologies used in these spectroscopic analyses, highlighting advancements in technology. There are many applications of these techniques across various fields such as medical diagnostics, agriculture, food processing, environmental monitoring, and industrial quality control. This chapter mainly discusses the applications of techniques in food products. Emphasis is placed on the strengths and limitations of each method, providing a comprehensive understanding of how these optical spectroscopic techniques can be effectively utilized for qualitative and quantitative analysis of complex samples. The chapter also address the challenge associated with high equipment costs, offering insights into future directions and innovations in the field of spectroscopy.