This book explores the interaction between nitric oxide (NO) and ferritin, a protein essential for the regulation of iron in the body. Nitric oxide, produced by macrophages during inflammation, plays a key role in various biological processes such as vasodilation and immune responses. Ferritin is crucial for maintaining iron levels, preventing imbalances that can lead to disorders including Biermer anemia. The book analyzes how NO modifies ferritin, affecting its ability to store and release iron, and uses X-ray absorption spectroscopy (XAS) to illustrate these structural changes. In conclusion, the book underlines the importance of this research for a better understanding of the underlying mechanisms, and suggests further investigations in this field.