Abstract: The 3-D morphology of bainite in steels has been studied by SEM with high resolution. Based on the dual-surface observation results, the bainite is divided into three sub-categories:upper,transient and lower bainites. The subplates composing upper bainite sheaf are lath-like while the whole morphology of lower bainite and that of its subplates are plate-shaped. The subunits in lower bainite seem to be lumpish. The 3-D morphology of transient bainite proves to resemble both upper and lower bainites on some aspects. The microStructural evolution of three types of bainite has been discussed.