Rusts of iron and steels have been so familiar to us since the ancient Iron Age. Over the last decades, substantial progress has been made in understanding the formation of rust and its structure. Techniques for controlling the structures and properties of rust layers have also been developed that are capable of protecting steel surfaces from atmospheric corrosion. In this article, we mention first what rusting is, and then the structures including [rust/steel] interfacial structure and protective ability of rust layers. Latest rust controlling technologies are also shown.