Leukaemia. False-colour scanning electron microgr- aph of white blood cells (yellow) & a red blood cell from a chronic lymphocytic leukaemia (CLL) patient. The white cells are B lymphocytes, though in a minority of CLL cases they may be T lymphocytes. CLL cell surfaces have numerous microvilli, as seen here. Leukaemia is a malignant disease in which the bone marrow & other blood- forming organs overproduce certain types of white cells. These immature & abnormal cells suppress normal production of white & red cells, increasing susceptibility to other infections. Magnification: x1800 at 35mm size, x4860 at 6x6cm size.