Explore spectroscopy techniques using NV centers in diamond when subjected to off-axis magnetic fields in this 45-minute lecture. Delve into the principles of precision measurements and quantum metrology as part of a comprehensive program organized by the International Centre for Theoretical Sciences. Gain insights into the application of quantum physics in emerging technologies, including quantum computers, sensors, and encryption tools. Learn about the theory of precision measurements, estimation techniques, and both classical and quantum metrology. Discover how atomic and optical physics techniques are utilized for quantum metrology and precision measurements, with a focus on systems such as atoms, ions, molecules, photons, and NV-centers. Suitable for advanced physics students, PhD candidates, and researchers, this lecture contributes to building knowledge and awareness in the field of quantum measurement and sensing technology.