Granules are granule-shaped deposits in biological cells that are clearly visible under the microscope and usually contain storage or secretion substances (e.g. glycogen , lipid , protein , ferritin or pigment granules). They are surrounded by a non-uniform membrane that separates the granule content from the cytoplasm . They can be differentiated into acidophilic, azurophilic, chromaffinic, basophilic, eosinophilic, metachromatic and neutrophilic based on their stainability .
The release of granules from the cells is called degranulation .