Eosinophil is also known as eosinophilic granulocyte, or eo. Eosinophils are one of the easiest cells in the peripheral blood to recognize because of their large bright granules. The diameter of the eosinophil is 9-15 microns, and the N:C ratio is 1:3. Eosinophils are generally the largest granulocytes found in normal blood.