In the past, the crystallographic relationship between the gamma-phase and the alpha-phase in isotactic Polypropylene (i-PP) was extensively studied and established via i-PP oligomers of which the gamma-phase can be formed at atmospheric pressure. We attempt to investigate how the epitaxial domination of the crystal morphologies takes place in the gamma-phasc of chain-folded crystals using high molecular weight i-PP, samples with a controlled number of stereodefects. These specifically synthesized samples favor the isothermal growth of the gamma-phase crystals from a thin Film melt at 100-140 degrees C at atmospheric pressure. It is known that the gamma-phase unit cell has the very unique Characteristic of all orthohombic lattice with alternating stein orientations in every two stem layers along the c-axis. Due to the specific epitaxial growth of the gamma-phase on the elongated alpha-phase single crystals, two different morphologies were identified via transmission electron and atomic force microscopies (TEM and AFM). The First gamma-phase crystalline morphology is needle-like. The selected area electron diffraction (SAED) results showed that either the [(1) over bar 10] or [110] zone axis was parallel to the thin film normal, and the needle direction was along the c-axis of the gamma-phase. The epitaxial growth of this type of gamma-phase crystal was generated from the stein direction in file initial alpha-phase single crystal being parallel to the thin film (and thus, the lamellar) normal. In this case, the stein length of the alpha-phase single crystal provided a limit for the growth of the gamma-phase to develop toward the thin film normal. On the other hand, the stem length oriented at +/-80 degrees away from the film normal in the gamma-phase crystal was limited by the folded chain crystal growth kinetics, which is proportional to the reciprocal supercooling. These two factors thus resulted in the formation of these peculiar needle-like crystals. The second gamma-phasc crystalline morphology was "flat" lamellae. The SAED results indicated that the chain orientations in the "flat" lamellae were tilted at +/-40 degrees from the thin film normal within the ab-plane of the gamma-phase. Macroscopically, growth of the "flat" lamellae was thermodynamically more stable compared with the needle-like crystals due to their larger crystal size. On the basis of the tilted SAED and dark field results from TEM, the microscopic formation mechanism of this morphology revealed that the initial alpha-phase single crystal had to have a stern orientation tilted +/-25 degrees away from the thin film normal within the alpha-plane around the b-axis. Therefore. the epitaxial growth of the gamma-phasc oil the ac-plane of the alpha-phase did not possess a chain orientation of +/-40 degrees from the thin film normal. The final "flat" lamellar gamma-phase crystals might have resulted from a continuous twist of the chain orientation from + 25 degrees/-55 degrees or -25 degrees/+ 55 degrees to +/-40 degrees from the thin Film normal.