This book presents a comprehensive overview of functional food science and its growing importance in health research. The field addresses how specific food derived compounds influence biological processes that relate to major lifestyle related diseases such as cancer, cardiovascular disorders, and metabolic syndrome. The content covers a wide range of themes that include molecular mechanisms, analytical methods, clinical insights, and newly emerging scientific concepts. Topics such as metabolomics, imaging mass spectrometry, non coding RNA pathways, brain?gut interactions, chrononutrition, and the hormesis effect help readers understand how functional food factors work within the body. The book also examines practical applications, disease focused research, and potential side effects of food derived bioactive substances. Structured into eight parts, the volume offers reflections from senior scientists, detailed thematic chapters, and broad discussions that connect basic research with applied outcomes. It is suitable for academic researchers, industry specialists who develop functional food products, and graduate students who study food functionality.