Light micrograph of human blood showing deformed red blood cells in sickle cell anaemia. The disease is characterised by the production of abnormal haemoglobin (Hbs) in the red blood cells (erythrocytes). Hbs is insoluble, and when it precipitates the normally biconcave erythrocytes are distorted into the characteristic sickle shape; such cells are rapidly removed from the circulation, resulting in anaemia. Magnification: x270 at 35mm size.