Epigenomics is the study of heritable and reversible alterations to the genome that affect gene expression without changing the genetic sequence and has emerged as a critical field in modern biology. Unlike genetics, which focuses on DNA sequence variations, epigenomics explores regulatory mechanisms including histone modifications, DNA methylation, non-cording RNAs, and chromatin remodeling that affect cellular function as well as growth. These epigenetic modifications play a fundamental role in cellular differentiation, genome stability, and response to environmental stimuli. The relationship between genomes and epigenomics is crucial for knowing various biological processes, such as disease progression and therapeutic innervations. Improvements in sequencing methods and computational tools and techniques have markedly augmented our capacity to map that examine epigenomic landscapes across many species and situations. Comparative epigenomics has revealed evolutionary conservation and species-specific adaptations that impact gene regulation. Furthermore, environmental and lifestyle factors contribute to epigenomic variability, influencing health outcomes. This chapter provides a comprehensive overview of key epigenetic mechanisms, their implications in disease, and the latest advancements in epigenomic research, highlighting the potential for personalized medicine and therapeutic applications.