Elements that were once laboratory curiosities, like neodymium, tellurium, and terbium, now figure centrally when novel energy systems are discussed. Many of these elements are not at present mined, refined, or traded in large quantities. New technologies can only impact our energy needs, however, if they can be scaled from laboratory, to demonstration, to massive implementation. As a result, some previously unfamiliar elements will be needed in great quantities. Although every element has its unique story, these Energy Critical Elements have many features in common. I will describe the shared characteristics of these elements, their roles in emerging technologies, potential constraints on their availability, and government actions that can help avoid disruptive shortages. As an example, I will focus especially on elements that are required for photovoltaic technologies.