Final answer:
Stained leukocytes without clearly visible granules are known as agranular leukocytes. This category includes lymphocytes and monocytes, which have smaller, less visible granules compared to granular leukocytes such as neutrophils, eosinophils, and basophils.
Step-by-step explanation:
Stained leukocytes with no clearly visible granules are called agranular leukocytes. Agranular leukocytes, such as lymphocytes and monocytes, contain smaller and less noticeable granules in their cytoplasm compared to granular leukocytes. Granular leukocytes, which include neutrophils, eosinophils, and basophils, have distinct and abundant granules that are easily visible when stained. Unlike granular leukocytes, agranular leukocytes have a simpler shape of nucleus, sometimes indented, but without distinct lobes.