Chromium has been known to be a micronutrient for mammals for four decades, but progress in elucidating the role of chromium has proceeded slowly. However, recent studies have shed light on a potential role of chromium in maintaining proper carbohydrate and lipid metabolism at a molecular level. The oligopeptide chromodulin binds chromic ions in response to an insulin-mediated chromic ion flux, and the metal-saturated oligopeptide can bind to an insulin-stimulated insulin receptor, activating the receptor's tyrosine kinase activity. Thus, chromodulin appears to play a role in an autoamplification mechanism in insulin signaling. The molecular agent responsible for transporting chromium from mobile pools to insulin-sensitive cells is probably the metal transport protein transferrin. Chromium from the popular dietary supplement chromium picolinate enters cells via a different mechanism. Release of chromium from chromium picolinate for use in cells requires reduction of the chromic center, a process that can lead potentially to the production of harmful hydroxyl radicals.