Everyone knows about bones. It doesn't take very long walking around on earth before we learn about x-rays and skeletons. Casts and calcium. We understand. Bones are important. They give us structure and form. Two really important things. What we don't hear as much about is the stuff inside the bones -- the marrow, which is a major site of blood cell production. Our bodies' strength and vitality springs forth from here. Equally as important, but not equally recognized. Read next feature >