Martensite is a hard, brittle phase of steel that forms when austenite, a softer phase, is rapidly cooled or quenched. This transformation occurs during processes like heat treatment, where the steel is heated to high temperatures and then cooled quickly to achieve desired properties. The structure of martensite is characterized by a distorted arrangement of atoms, which contributes to its hardness. While martensite enhances strength and wear resistance, it can also make the material more susceptible to cracking. Understanding martensite is crucial in metallurgy for developing high-performance steel used in various applications.