No matter where we are and what we are doing, steel is always present in our lives, at work or in our leisure time, sometimes even as a work of art. Steel is indispensable, recyclable and has a very special significance: In our modern industrial society, steel is the basic material for all important industrial sectors, such as automotive and shipbuilding, apparatus and mechanical engineering, bridge and structural steel engineering, energy and environmental technology, the packaging industry, the household and sports industry, medical technology, hydraulics and pneumatics, and many more. Today, the large-scale production and processing of steel is state of the art and the variety of steels developed is impressive. This world of steel is constantly evolving and has become astonishingly diverse, indeed so complex that it is not easy to keep track of in practice. The aim is to give the reader an understanding of this world, not in a highly scientific way, but in a technically correct and easily understandable way: from steel production, ingot and continuous casting, forming and mechanical processing to finishing, testing and packaging of the products, the processes and equipment predominantly used throughout, including the environmentally compatible recycling and disposal of waste. Interesting applications will also be pointed out.