Neutrophils are the primary immune cells that fight pathogens in organisms ranging from slime molds to mammals. They are recruited to sites of infection, recognize and phagocytose microbes, and kill pathogens through cytotoxic mechanisms such as the production of reactive oxygen species, release of antimicrobial peptides, and the formation of neutrophil extracellular traps (NETs). These functions also play key roles in tissue injury and are involved in various inflammatory and autoimmune diseases. Neutrophils communicate with other immune cells, such as macrophages and dendritic cells, to amplify pathologic inflammation. Neutrophil homeostasis is regulated by cytokines like G-CSF and GM-CSF, as well as by the balance between neutrophil production and turnover. Neutrophil recruitment involves a multistep process, including adhesion, rolling, and transmigration through the endothelium. Neutrophil activation is a multistep process that leads to the release of granule proteins, phagocytic capabilities, and the production of NETs. Neutrophils recognize pathogens through pattern-recognition receptors and opsonic receptors, which trigger intracellular signals leading to pathogen-killing capacity. Neutrophils kill pathogens through phagocytosis, production of reactive oxygen species, and fusion of granules with the phagosome. Neutrophil antimicrobial peptides, such as α-defensins and cathelicidins, play a critical role in host defense. Neutrophil extracellular traps (NETs) are formed by the release of decondensed chromatin and granule-derived antimicrobial components, which can cause tissue injury and stimulate immune reactions. The study of neutrophil functions is important for understanding disease progression and developing therapeutics to prevent neutrophil-mediated damage to host tissues.Neutrophils are the primary immune cells that fight pathogens in organisms ranging from slime molds to mammals. They are recruited to sites of infection, recognize and phagocytose microbes, and kill pathogens through cytotoxic mechanisms such as the production of reactive oxygen species, release of antimicrobial peptides, and the formation of neutrophil extracellular traps (NETs). These functions also play key roles in tissue injury and are involved in various inflammatory and autoimmune diseases. Neutrophils communicate with other immune cells, such as macrophages and dendritic cells, to amplify pathologic inflammation. Neutrophil homeostasis is regulated by cytokines like G-CSF and GM-CSF, as well as by the balance between neutrophil production and turnover. Neutrophil recruitment involves a multistep process, including adhesion, rolling, and transmigration through the endothelium. Neutrophil activation is a multistep process that leads to the release of granule proteins, phagocytic capabilities, and the production of NETs. Neutrophils recognize pathogens through pattern-recognition receptors and opsonic receptors, which trigger intracellular signals leading to pathogen-killing capacity. Neutrophils kill pathogens through phagocytosis, production of reactive oxygen species, and fusion of granules with the phagosome. Neutrophil antimicrobial peptides, such as α-defensins and cathelicidins, play a critical role in host defense. Neutrophil extracellular traps (NETs) are formed by the release of decondensed chromatin and granule-derived antimicrobial components, which can cause tissue injury and stimulate immune reactions. The study of neutrophil functions is important for understanding disease progression and developing therapeutics to prevent neutrophil-mediated damage to host tissues.