From the perspective of macroscopic organization, there are two types of bone:

Compact or cortical bone:
constituted by the haversian or osteonal system. It consists of deposits of concentric layers around a central canal (the figure shows birefringence in unstained samples under polarized light). It constitutes the external part of bone structures. Cortical bone is dense and compact, making up about 80% of the skeleton. Its main function is to provide mechanical support and protection; it also participates in metabolic functions to a lesser extent and over longer periods of time than cancellous bone.

Trabecular or cancellous bone:
This constitutes the internal part of bone, especially the epiphysis of long bones, vertebrae and the iliac bone. It presents a 3-dimensional arrangement of trabeculae for mechanical purposes, with bone marrow within it (the figure shows a Masson-Goldner stained section of the iliac bone with both trabecular and cortical components). In addition to providing mechanical support, it is the most metabolically active type of bone.