Under magnification you can clearly see the system of concentric circles that forms compact bone. You can think of compact bone as being very similar to a bundle of cut trees or logs. Each 'log,' or long cylindrical unit, is called an osteon and, just like trees, osteons have rings of growth. Now, unlike trees, you can't figure out a person's age by counting their 'growth rings,' called lamellae, but they do grow like the rings of a tree