Microglia are a type of glial cell that are found in the central nervous system, which includes the brain and spinal cord. They are the resident immune cells of the brain and play a crucial role in its defense and maintenance. Microglia are the smallest cells in the brain and are characterized by their small, round shape and numerous fine branches. They constantly survey their surroundings, monitoring for any signs of infection, injury, or abnormalities. When activated, microglia can change their shape and release various substances to help fight off pathogens, remove damaged cells, and promote tissue repair. They also contribute to the regulation of brain development, synaptic pruning, and the maintenance of healthy neuronal connections.