Because blood cells are made in the bone marrow, a bone marrow biopsy is a way of going straight to the source in order to get the highest possible quality of diagnostic information. I would expect that the sample will be examined by a pathologist using a microscope. DNA will be extracted from certain cells and analyzed.

Getting a bone marrow biopsy is not something you would want to do as a hobby, but it is doable. They use a lot of lidocaine (a local anesthetic), and they probably will offer you other medications too to make it easier for you. I have had a half dozen or so. Afterwards, it makes a good story you can use to impress your friends.