During cancer care, doctors may collect a sample of a patient's bone marrow to see how well these cells develop and work. This testing is called a bone marrow aspiration or a bone marrow biopsy. It can be done to diagnose some types of cancer, learn more about a diagnosis, or monitor cancer treatment.

Bone marrow is the spongy, fatty tissue inside your body's larger bones. It has liquid and solid parts.

Bone marrow makes these types of blood cells:

• Red blood cells carry oxygen to all parts of the body.