This chapter gives the description on hematology, which is given in the question and answer format. A hemoglobin molecule is conjugated protein composed of iron containing pigment called heme and protein globin. About 65–70% of hemoglobin is synthesized in normoblasts and 30–35% is synthesized at the reticulocyte stage. This chapter covers the anemia, iron deficiency anemia (IDA), macrocytic anemia, pernicious anemia, hemolytic anemia, defects in hemoglobin production, sickle cell disease, hereditary spherocytosis, thalassemia syndrome, glucose-6-phosphate dehydrogenase (G6PD) deficiency, miscellaneous anemia, non-neoplastic disorders of WBC, acute leukemia, chronic myeloid leukemia, chronic lymphocytic leukemia, myeloproliferative neoplasms, plasma cell neoplasms, Hodgkin lymphoma, hemostasis, bleeding disorders (hemorrhagic diatheses), thrombocytopenia, qualitative platelets defects, immune thrombocytopenic purpura, thrombocytosis, disorders of coagulation (clotting), fibrinolysis, microangiopathic hemolytic states and thrombocytopenia, disseminated intravascular coagulation (DIC), transfusion medicine, complications of blood transfusion, stem cells, hematopoietic cell (HSC) transplantation, drugs used in hematological diseases, and spleen.