I can feel it in my bones....

Sperm Cells Created From Human Bone Marrow:

Human bone marrow has been used to create early-stage sperm cells for the first time, a scientific step forward that will help researchers understand more about how sperm cells are created.

Gives a new meaning to the word "boner", doesn't it? OK, too late at night - I am losing all sense of what is appropriate on a science blog. Actually, the study is interesting besides its potential for humor.