Probiotics, defined as “live microorganisms which, when administered in adequate amounts, confer a health benefit on the host,” have evolved beyond their traditional use in digestive health to become a key area of research in preventive and therapeutic medicine. Originally associated with fermented dairy products, probiotics now span a wide spectrum of delivery systems including encapsulated supplements, functional foods, beverages, and even dermatological applications. Recent research has expanded our understanding of the human microbiome, leading to novel insights into how probiotics influence systemic health, including metabolic, immunological, neurological, and dermatological functions. Advances in sequencing technologies and metabolomics have enabled strain-specific identification and functional profiling, allowing for the development of next-generation probiotics such as Akkermansia muciniphila, Faecalibacterium prausnitzii, and genetically engineered strains with targeted functions. Studies have shown that certain probiotics can improve insulin sensitivity, reduce markers of inflammation, modulate the gut-brain axis to alleviate symptoms of anxiety and depression, and enhance immune responses, particularly in the context of respiratory infections and vaccine efficacy. The emerging field of psychobiotics—probiotics that affect mental health—is gaining particular traction. The timeless quote by Hippocrates, “Let food be thy medicine and medicine be thy food,” is especially applicable to probiotics, as these microorganisms exemplify how nutrition can be leveraged for therapeutic benefit. Moreover, the commercial landscape of probiotic products has rapidly diversified. Innovations include synbiotics (combinations of prebiotics and probiotics), postbiotics (non-viable microbial cells or components that confer health benefits), and precision probiotics tailored to individual microbiomes. Regulatory frameworks are also evolving, with increasing emphasis on clinical validation and transparent strain labelling. This review aims to synthesize the latest scientific findings on the multifaceted health benefits of probiotics, highlight the technological advances in probiotic formulations, and critically assess the challenges in standardization, efficacy, and safety.