Hematology is the study of blood and related organs, such as the spleen and lymph nodes. It involves the diagnosis and treatment of diseases that affect the production of blood and its components, such as red and white blood cells, platelets, and hemoglobin. Hematologists specialize in the diagnosis and treatment of blood disorders, including anemia, leukemia, and hemophilia. They also diagnose and treat conditions related to the immune system, such as autoimmune diseases and lymphoma.