Microglia, the resident immune cells of the brain, play a critical role in neurodegenerative diseases by producing toxic factors such as TNF-α, nitric oxide, IL-1β, and reactive oxygen species (ROS), which contribute to progressive neuronal damage. Chronic microglial activation, either from a single stimulus or repeated exposure, leads to sustained neuronal loss. Microglia are unique in their origin, derived from myeloid lineage cells in the bone marrow, and they maintain homeostasis in the central nervous system (CNS). In their resting state, microglia have a ramified morphology and low expression of MHC proteins, but they become activated in response to injury, inflammation, or disease, leading to morphological changes and the release of pro-inflammatory factors. Microglia are essential for normal CNS function, including phagocytosis of cellular debris, synaptic plasticity, and trophic support for neurons. However, when microglia become chronically activated, they can shift to a pro-inflammatory phenotype, releasing toxic factors that damage neurons. This is particularly evident in neurodegenerative diseases such as Parkinson's disease (PD), where microglial activation is linked to the progressive loss of dopaminergic neurons. In PD, microglial activation is associated with the release of cytokines, ROS, and other neurotoxic molecules, contributing to neuronal death. Lipopolysaccharide (LPS) is a potent stimulus for microglial activation, leading to the production of ROS and pro-inflammatory factors that exacerbate neurodegeneration. Microglial activation can be further exacerbated by environmental toxins, disease proteins, and neuronal damage. The NADPH oxidase enzyme plays a key role in microglial ROS production, which contributes to neurotoxicity. In PD, microglial activation is linked to the release of toxic factors that damage dopaminergic neurons, and the activation of microglia can be sustained even after the initial stimulus has subsided. Chronic microglial activation is a key driver of neurodegenerative diseases, with microglia playing a central role in the progression of conditions such as Alzheimer's disease, multiple sclerosis, and HIV-associated neurocognitive disorder. The mechanisms underlying microglial activation and its role in neurodegeneration are complex, involving redox signaling, cytokine production, and the release of toxic factors. Understanding these mechanisms is crucial for developing therapeutic strategies to mitigate neuroinflammation and slow the progression of neurodegenerative diseases.Microglia, the resident immune cells of the brain, play a critical role in neurodegenerative diseases by producing toxic factors such as TNF-α, nitric oxide, IL-1β, and reactive oxygen species (ROS), which contribute to progressive neuronal damage. Chronic microglial activation, either from a single stimulus or repeated exposure, leads to sustained neuronal loss. Microglia are unique in their origin, derived from myeloid lineage cells in the bone marrow, and they maintain homeostasis in the central nervous system (CNS). In their resting state, microglia have a ramified morphology and low expression of MHC proteins, but they become activated in response to injury, inflammation, or disease, leading to morphological changes and the release of pro-inflammatory factors. Microglia are essential for normal CNS function, including phagocytosis of cellular debris, synaptic plasticity, and trophic support for neurons. However, when microglia become chronically activated, they can shift to a pro-inflammatory phenotype, releasing toxic factors that damage neurons. This is particularly evident in neurodegenerative diseases such as Parkinson's disease (PD), where microglial activation is linked to the progressive loss of dopaminergic neurons. In PD, microglial activation is associated with the release of cytokines, ROS, and other neurotoxic molecules, contributing to neuronal death. Lipopolysaccharide (LPS) is a potent stimulus for microglial activation, leading to the production of ROS and pro-inflammatory factors that exacerbate neurodegeneration. Microglial activation can be further exacerbated by environmental toxins, disease proteins, and neuronal damage. The NADPH oxidase enzyme plays a key role in microglial ROS production, which contributes to neurotoxicity. In PD, microglial activation is linked to the release of toxic factors that damage dopaminergic neurons, and the activation of microglia can be sustained even after the initial stimulus has subsided. Chronic microglial activation is a key driver of neurodegenerative diseases, with microglia playing a central role in the progression of conditions such as Alzheimer's disease, multiple sclerosis, and HIV-associated neurocognitive disorder. The mechanisms underlying microglial activation and its role in neurodegeneration are complex, involving redox signaling, cytokine production, and the release of toxic factors. Understanding these mechanisms is crucial for developing therapeutic strategies to mitigate neuroinflammation and slow the progression of neurodegenerative diseases.