Degranulation is a cellular process that releases antimicrobial cytotoxic or other molecules from secretory vesicles called granules found inside some cells. It is used by several different cells involved in the immune system, including granulocytes (neutrophils, basophils, and eosinophils) and mast cells. It is also used by certain lymphocytes such as natural killer (NK) cells and cytotoxic T cells, whose main purpose is to destroy invading microorganisms.