Microglia are the brain’s main neuroimmune cells. They are armed with a variety of genes to carry out three primary functions: a sentinel function that that monitors changes in the environment, a housekeeping function that promotes normal neuronal operation and well-being, and a defense function that responds to changes and provides neuroprotection. If chronically activated, they have the capacity to damage and destroy neurons and contribute to neurodegenerative conditions such as Alzheimer’s Disease, Parkinson’s Disease, and Huntington’s Disease.