This presentation explores the applications of X-ray Absorption Spectroscopy (XAS) in studying phase change materials (PCMs). It begins with an introduction to synchrotron radiation, explaining its generation, properties, and the anatomy of a synchrotron beamline. The core of the presentation focuses on XAS fundamentals: XANES for valence state and local symmetry analysis. EXAFS for quantitative structural information, such as interatomic distances and coordination numbers. The LISA beamline at ESRF is highlighted, showcasing its experimental capabilities and setup for XAS measurements. Experimental examples include studies on: GST (Ge₂Sb₂Te₅) polymorphism, comparing as-deposited, melt-quenched, and ion-implanted amorphous phases. Resistance drift in amorphous GeTe, revealing structural changes over time. Superlattice structures in (GeTe)₂/(Sb₂Te₃)ₘ systems, identifying intermixing effects. Ovonic threshold switching in GeSe-based materials, linking structural and electrical properties. The presentation concludes by emphasizing XAS as a powerful tool for probing local structure and validating theoretical models in PCMs.