The gut microbiota, a complex community of microorganisms residing in the gastrointestinal tract, plays a crucial role in human health and disease. Recent advances in 'omic' technologies have significantly enhanced our understanding of the gut microbiota's composition and functions, revealing its influence comparable to a new organ. The gut microbiota is now recognized as an essential component of the human body, interacting with the host's physiology and immune system. It can promote health but also contribute to disease, particularly in conditions such as inflammatory bowel disease (IBD), obesity-related diseases, liver disease, and colorectal cancer (CRC). The gut microbiota is influenced by various factors, including diet, antibiotics, and surgery. Manipulating the microbiota through interventions such as probiotics, prebiotics, polyphenols, and fecal microbiota transplantation (FMT) has shown potential in treating and preventing diseases. For instance, probiotics, which are live microorganisms, can confer health benefits by modulating the gut microbiota. Prebiotics, which are non-digestible carbohydrates, promote the growth of beneficial bacteria. Polyphenols, plant-derived compounds, can modulate the gut microbiota to promote a healthier profile. In obesity-related diseases, the gut microbiota is associated with changes in the Firmicutes:Bacteroidetes ratio, which may influence weight and metabolic health. Studies have shown that the microbiota of obese individuals differs from that of lean individuals, and interventions such as diet can alter the microbiota composition and improve metabolic status. In liver diseases, the gut microbiota contributes to inflammation and disease progression, and probiotics and FMT have shown promise in ameliorating liver injury. In IBD, the gut microbiota is altered, with a reduction in Firmicutes and an increase in Bacteroidetes. The microbiota's role in IBD pathogenesis is complex, and interventions such as probiotics and FMT have shown potential in managing the disease. In CRC, the microbiota plays a significant role in tumor development, with certain bacteria contributing to oncogenic processes. The microbiota's metabolic functions, including the metabolism of fiber and sulfate, are critical in CRC development. Overall, the gut microbiota is a dynamic system that interacts with the host and influences various diseases. Understanding the microbiota's role in health and disease is essential for developing new therapeutic strategies and personalized healthcare approaches.The gut microbiota, a complex community of microorganisms residing in the gastrointestinal tract, plays a crucial role in human health and disease. Recent advances in 'omic' technologies have significantly enhanced our understanding of the gut microbiota's composition and functions, revealing its influence comparable to a new organ. The gut microbiota is now recognized as an essential component of the human body, interacting with the host's physiology and immune system. It can promote health but also contribute to disease, particularly in conditions such as inflammatory bowel disease (IBD), obesity-related diseases, liver disease, and colorectal cancer (CRC). The gut microbiota is influenced by various factors, including diet, antibiotics, and surgery. Manipulating the microbiota through interventions such as probiotics, prebiotics, polyphenols, and fecal microbiota transplantation (FMT) has shown potential in treating and preventing diseases. For instance, probiotics, which are live microorganisms, can confer health benefits by modulating the gut microbiota. Prebiotics, which are non-digestible carbohydrates, promote the growth of beneficial bacteria. Polyphenols, plant-derived compounds, can modulate the gut microbiota to promote a healthier profile. In obesity-related diseases, the gut microbiota is associated with changes in the Firmicutes:Bacteroidetes ratio, which may influence weight and metabolic health. Studies have shown that the microbiota of obese individuals differs from that of lean individuals, and interventions such as diet can alter the microbiota composition and improve metabolic status. In liver diseases, the gut microbiota contributes to inflammation and disease progression, and probiotics and FMT have shown promise in ameliorating liver injury. In IBD, the gut microbiota is altered, with a reduction in Firmicutes and an increase in Bacteroidetes. The microbiota's role in IBD pathogenesis is complex, and interventions such as probiotics and FMT have shown potential in managing the disease. In CRC, the microbiota plays a significant role in tumor development, with certain bacteria contributing to oncogenic processes. The microbiota's metabolic functions, including the metabolism of fiber and sulfate, are critical in CRC development. Overall, the gut microbiota is a dynamic system that interacts with the host and influences various diseases. Understanding the microbiota's role in health and disease is essential for developing new therapeutic strategies and personalized healthcare approaches.