Bone marrow biopsy and bone marrow aspiration are procedures to collect and examine bone marrow; the spongy tissue inside some of your larger bones.Bone marrow biopsy and aspiration can show whether your bone marrow is healthy and making normal amounts of blood cells. Doctors use these procedures to diagnose and monitor blood and marrow diseases, including some cancers, as well as fevers of unknown origin.Bone marrow has a fluid portion and a more solid portion. In bone marrow biopsy, your doctor uses a needle to withdraw a sample of the solid portion. In bone marrow aspiration, a needle is used to withdraw a sample of the fluid portion.Bone marrow biopsy and bone marrow aspiration are often done at the same time. Together, these procedures may be called a bone marrow exam.