These are a group of white blood cells that have many and well-pigmented granules, and derive from the bone marrow myeloblasts. The granules are sources of digestive, immunologic, and inflammatory proteins. The classic granulocytes are neutrophils, eosinophils, and basophils, but one should also include mast cells. Also, macrophages, which start out as agranulocytic monocytes but get lots of granules when they grow up.