Petroleum is a complex mixture of liquid hydrocarbons that results from the anaerobic decomposition of organic matter, such as marine plankton and other microscopic organisms. Over immense geological timescales, the accumulating biomass is subjected to high temperatures and immense pressure within subterranean rock formations, initiating chemical reactions that transform the material into liquid and gaseous compounds. The resulting mixture contains various alkanes, cycloalkanes, and aromatics, classified by their molecular structure and boiling points. The physical properties of petroleum are crucial for its industrial application, as the variations in its chemical composition determine its potential for refining into usable fuels and petrochemical feedstock.