Steam crackers are the heart of modern petrochemistry. They represent the most important source of petrochemical raw materials. With the help of steam, naphtha, which consists of longer hydrocarbon chains, is cracked. The process consists of several steps: first, the raw gasoline is mixed with steam and evaporated. It is then briefly heated to over 800 °C in large furnaces causing the naphtha to decompose into smaller building blocks such as ethylene and propylene, which are central building blocks for many more processes. The reaction mixture is then separated in several steps and the products are further processed using a variety of chemical processes.