vary in their proportions of compact and cancellous (spongy) bone; compact bone is dense and solid in appearance whereas cancellous bone is characterized by open space partially filled with needle-like structures.
You find cancellous bone in a number of places: the medullary cavity of long bones. And inside short flat (as pictured above) and irregular bones.
Long bone examples are the femur tibia and humerus. The bones of the skull are flat as well as the sternum. Often marrow taps are done on the sternum.