A diagnostic procedure in which a solid sample (core biopsy) of bone marrow (usually from the posterior iliac bone) and a liquid sample of marrow (aspirate) are taken for microscopic examination. The examination assesses the histological structure (histochemistry) of the marrow, the ratio of fat cells to hematopoietic cells (cells), the presence, proportion, and integrity of hematopoietic precursors (myelocytes, red blood cells, platelets), and detects abnormal cells, tumors, fibrosis, or storage diseases.