A recent report by the American Physical Society (APS) and Materials Research Society (MRS) defines energy critical elements (ECE) as:"a class of chemical elements that currently appear critical to one or more new, energy-related technologies. A shortage of these elements would significantly inhibit large-scale deployment, which could otherwise be capable of transforming the way we produce, transmit, store, or conserve energy."Located primarily around the center of the Periodic table, there are several reasons why these elements may be considered critical beyond the role they play in electronics and advanced technologies such as electric cars, wind turbines and photovoltaic cells. The joint APS and MRS study explains elements may be critical because they might be "intrinsically rare in Earth's crust, poorly concentrated by natural processes, or currently unavailable in the United States." While many energy critical elements also play important roles in national defense, this hearing is primarily focused on the commercial and energy applications of these materials.