Cancellous bone is composed of interlacing fragments of bone, known as spicules or trabeculae, that form a branching interconnected structure. Between the interconnected branches of the trabecular bone is marrow space. Bone is composed of 2 kinds of materials, organic and inorganic. The inorganic component is primarily calcium appatite, a form of calcium phosphate. The inorganic component is predominantly collagen.
Normal bone is too hard to be cut for histological sectioning.
It therefore has to be demineralized by soaking it in acid solutions to remove the calcium apatite. What is left behind is demineralized bone matrix, referred to as osteoid. Osteoid, being composed of collagen, stains pink. If the bone is improperly or incompletely demineralized, you will find that it stains a bluish color because of the calcium apatite. Normal healthy living bone contains within it lacunae which contain osteocytes.