This book explores isotopes which are vital to the science and technology base of the U.S. economy. Isotopes, both stable and radioactive, are essential tools in the growing science, technology, engineering and health enterprises of the 21st century. The scientific discoveries and associated advances made as a result of the availability of isotopes today span widely from medicine and biology, physics, chemistry and a broad range of applications in environmental and material sciences. Isotope issues have become crucial aspects of homeland security. Isotopes are utilised in new resource development, in energy from bio-fuels, petrochemical and nuclear fuels, in drug discovery, health care therapies and diagnostics, in nutrition, in agriculture and in many other areas.