text: The diffusive theory of bainite's transformation process is based on the assumption that a bainitic ferrite plate grows with a similar mechanism as Widmanstätten ferrite at higher temperatures. Its growth rate thus depends on how rapidly carbon can diffuse from the growing ferrite into the austenite. A common misconception is that this mechanism excludes the possibility of coherent interfaces and a surface relief. In fact it is accepted by some that formation of Widmanstätten ferrite is controlled by carbon diffusion and do show a similar surface relief.