The gut microbiota, consisting of trillions of microorganisms, plays a critical role in regulating host physiology, including metabolism, immune responses, and brain function. This chapter examines the microbiota-gut-brain axis, a multifaceted bidirectional communication system connecting gut microbial activity with central nervous system processes through immune pathways, metabolic byproducts, and neural circuits like the vagus nerve. The evolution of the gut microbiota throughout an individual’s life—from early developmental influences like birth mode and antibiotic use to changes associated with aging and neurodegenerative conditions—highlights its dynamic nature. The chapter reviews experimental approaches and microbiome-based interventions to demonstrate the influence of gut microbiota on neurological conditions such as autism spectrum disorder, anxiety, and Alzheimer’s disease. Finally, it emphasises the importance of advancing microbiome-targeted therapies, integrating emerging technologies, and clinical trials to develop personalised strategies for enhancing brain health through gut microbiome modulation.