The first refineries to process crude used existing coal oil refineries or were built where oil was found. Early refineries were simple device that used large horizontal thanks to heat oil to separate the volatile components. The world's first oil refinery opened at Ploiesti, Romania, in 1856, In the United States, the first refinery opened in 1861. Over subsequent decades, the development of electricity and the advent of the internal combustion engine significantly impacted the demand for refined products, with ever-increasing amounts of gasoline and diesel fuels required in place of kerosine. Air transportation and World War 2 created the need for high-octane aviation gasoline and, later, jet fuel. Today, petroleum refining is a mature industry with a well-established infrastructure and technology base, employing a complex array of chemical and physical processing facilities to transform crude oil into products that consumers valve.