What does bone marrow biopsy needle mean?

Bone marrow biopsy needle, like bone marrow puncture, is also a way to understand the bone marrow elephant, but biopsy is more detailed and comprehensive than puncture to understand the bone marrow status. And for some diseases such as myelofibrosis, then you only bone marrow aspiration, then often is dry extraction, can not extract bone marrow fluid. So a bone marrow biopsy is a further diagnostic tool. It's a further examination based on a bone marrow aspiration.