Calcification is a prominent feature of atherosclerosis, frequently associated with myocardial infarction and other adverse cardiovascular outcomes. Currently, calcification is widely viewed as an end-stage, degenerative process which is inevitable in advanced atherosclerosis. Pathologists, however, have long noted that calcification may occur early in atherosclerosis and, at times, may appear histologically identical to organized bone, including areas resembling bone marrow. These observations suggest that rather than being a passive process, atherosclerotic calcification may instead be an active, regulated process similar to that of osteogenesis. Using an in-vitro model of arterial calcification a subpopulation of artery wall cells, capable of producing hydroxyapatite mineral in vitro was discovered. This article discusses some of the cellular and molecular mechanisms of arterial calcification identified utilizing this in-vitro model of vascular calcification.