This paper reviews the various ferritic microstructures produced by austenite decomposition in continuously cooled low-carbon and ultralow-carbon steels and irons. Various terminologies used to identify the different ferritic microstructures and presented and related to several classification systems which have been developed for bainitic and ferritic microstructures in steels. Microstructural aspects are emphasized and discussed relative to transformation kinetics and mechanisms of austenite transformation to various morphologies of ferrite.