Cellular senescence is a conserved cellular program characterized by a permanent cell cycle arrest triggered by a variety of stressors. Originally described as a tumor-suppressive mechanism, it is now recognized to exert pleiotropic and context-dependent functions, contributing to key physiological processes such as embryogenesis and tissue repair, as well as to processes associated with aging and the development of age-related diseases. Unlike normal cells, senescent cells remain metabolically active despite their non-dividing state. They significantly impact their environment through the Senescence-Associated Secretory Phenotype (SASP), a complex mix of cytokines, growth factors, and proteases. This secretory profile can promote tissue repair and regeneration but, if persistent, contributes to chronic inflammation, fibrosis, and tissue dysfunction. Two major pathways primarily regulate senescence: the p53/p21 and p16^INK4a^/Rb axes. These respond to stress signals like DNA damage, oxidative stress, and oncogenic activation, enforcing stable cell cycle arrest to prevent uncontrolled proliferation. However, as senescent cells accumulate over time, their ongoing SASP activity disrupts tissue homeostasis, driving inflammation and age-related diseases. Recent advances in multi-omics technologies, including metabolomics, proteomics, and lipidomics, have provided deeper insights into the complex molecular changes within senescent cells, revealing new biomarkers and potential therapeutic targets. These approaches offer a comprehensive understanding of cellular senescence, but challenges remain in distinguishing the causal relationships within these data and translating findings into clinical applications. This review integrates recent multi-omics discoveries, highlighting their potential to refine our understanding of senescence and support the development of targeted interventions to extend healthspan and combat age-related pathologies.