Conversation so far:
What is the function of the osteon in bone?
Osteons are cylindrical structures that contain a mineral matrix and living osteocytes connected by canaliculi, which transport blood.
How big is an osteon?
Osteons are roughly cylindrical structures that are typically between 0.25 mm and 0.35 mm in diameter. Their length varies from several millimeters to around 1 centimeter.
What can the bone osteons tell us?
Osteons in a bone fragment can be used to determine the sex of an individual and age, as well as aspects of taxonomy, diet, health and motor history.

Question: what is the structure made of
Self-contained rewrite: What are osteons made of?