text: Bainite can essentially be regarded as martensite that tempers during the course of transformation. It forms at a higher temperature than martensite, and even the latter can autotemper. Because the transformation temperature is higher, the austenite itself is mechanically weak so that the shape deformation due to bainite is relaxed by the plastic deformation of the adjacent austenite. As a consequence, the growing plate of bainite is confronted by a forest of dislocations that eventually terminates its growth even before the plate has hit an austenite grain boundary. Plates of bainite can therefore be smaller than those of martensite in the same steel. The transformation then proceeds by a sub-unit mechanism involving the successive nucleation of new plates.