A method for the preparation of well-defined crystallites of Mgcl 2 -supported Ziegler-Natta catalysts on Si wafers has been developed. This has been achieved by the spin-coating of a MgCl 2 solution onto a flat Si wafer, followed by controlled crystal growth to give well-defined MgCl 2 . nEtOH crystallites. The growth of the crystallites on the flat silica facilitates their characterization using electron and scanning probe microscopy. The relative proportions of 120° and 90° edge angles indicate the preference for the formation of a particular crystallite face for the MgCl 2 . Polyethylene has been identified to be formed on the lateral faces of the crystallite.