Stable isotopes - which have a mass that is slightly different even though their chemical properties are the same - have caused a little bias in the existence ratio through the processes of the cycle of matter in the natural world, including the food chain. For more than half a century, stable isotopes of light elements - particularly those of carbon and nitrogen - have been extensively used for biogeochemical studies. In the late 1930s, the first mass spectrometer was designed for measuring isotopic variations in gas samples with extraordinary precision. Research showed the natural abundance of 13C, after which scientists realized that natural biological processes can be investigated on the basis of small variations in the relative abundance of carbon isotopes in nature. One of the most successful applications of the above-mentioned investigation method is in the field of ecology, and Dr. Eitaro Wada was the first to apply this method in ecological studies. Earth, Life and Isotopes introduces the latest techniques for measuring slight bias in the existence ratio - such as oxygen, carbon, and nitrogen - and compiles state-of-the-art research that uses these in various fields, such as ecology, hydrology, geochemistry, etc.