A complete blood count, often referred to as a CBC, is a common blood test. A CBC provides detailed information about three types of cells in your blood: red blood cells, white blood cells, and platelets. These blood cells are made in the bone marrow, the spongy tissue filling the center of your bones. Bone marrow in the skull, sternum (breast bone), ribs, vertebral column (backbone), and pelvis produces these blood cells.
For a detailed description follow this link.
http://www.cc.nih.gov/ccc/patient_education/pepubs/cbc97.pdf
