Macrophages are a type of immune cells. Their main function is to engulf and digest pathogens (i.e., microbes), foreign substances, and cell debris via phagocytosis. Macrophages are formed from monocytes and are mostly located in tissues acquiring different forms and features depending on the organ and tissue type. These cells are also important for the nonspecific innate immunity and activate adaptive immunity by introducing foreign antigens and recruiting lymphocytes. Finally, macrophages release cytokines and regulate immune response by coordinating the interactions between immune cells.