This book focuses on presenting a comprehensive understanding of the Kelvin probe technique, emphasizing its significance as a non-destructive and powerful tool for measuring the work function of metals and semiconductor surfaces. It brings together scattered knowledge by outlining essential fundamentals, key design considerations, and practical precautions required for the fabrication and assembly of Kelvin probe equipment. The content also highlights the expanding potential of the technique in emerging fields such as nano and bio systems, along with its applications in advanced experiments like Photoemission Yield Spectroscopy and Surface Photovoltage Spectroscopy. Additionally, the book offers valuable insights into real-world implementation, drawing from the process of designing and developing a Kelvin probe setup. Structurally, it integrates theoretical concepts with applied aspects, making it both informative and practical. This book is particularly useful for researchers, academicians, and professionals working in surface science, surface engineering, and related interdisciplinary areas, especially those interested in instrumentation, experimental techniques, and material characterization.