Gene Expression - From Code to Cure offers a comprehensive and forward-looking exploration of how modern molecular biology is transforming our understanding of disease and redefining therapeutic possibilities. From gene editing and RNA-based therapies to DNA repair mechanisms and epigenetic regulation, this book presents a unified view of the molecular processes that govern health, aging, and disease. This book integrates gene editing, cellular and RNA-based therapies, DNA repair biology, and epigenetic regulation into a unified framework that bridges fundamental science with clinical innovation. The first section introduces readers to modern genetic therapies, tracing the evolution of genome-editing technologies from early discoveries to advanced CRISPR-based platforms. It further surveys the rapidly expanding landscape of gene, cell, and RNA therapies, highlighting their growing impact in treating both monogenic and complex disorders. The second section focuses on genomic integrity and aging, examining how DNA damage, repair mechanisms, and epigenetic alterations shape cellular function over time. Special attention is given to nonhomologous end joining (NHEJ), a critical yet imperfect DNA repair pathway, and its role in cancer, immunodeficiency, neurodegeneration, and emerging therapeutic strategies. The final section explores epigenetic inheritance and metabolic regulation of gene expression, revealing how chromatin dynamics and metabolic cues influence immune memory, cellular identity, and intergenerational information transfer. Together, these chapters emphasize that gene expression is not static but dynamically shaped by molecular, environmental, and metabolic signals. By integrating these interconnected disciplines, Gene Expression - From Code to Cure provides a clear roadmap for translating molecular insights into transformative medical interventions. Designed for researchers, clinicians, students, and advanced learners, this book serves as both an authoritative reference and an inspiring vision of how decoding life at the molecular level can lead to cures once thought impossible.