“MultiScale Material Science for Energy and Environment (MSE2)” is an international joint unit (UMI) between CNRS and MIT at the center of a strategic association covering research, training and education in partnership with industry. The UMI aims at “bottom up” simulation and experimental verification of properties of complex multiscale materials — from atomic-scale to microns, and from nanoseconds to years. Materials with important technological, economic, energy and environmental applications will be addressed, including cement, ceramics, nuclear fuels, steels and geo-materials. The UMI hosts French researchers at MIT, each for a number of years, and is seen as a gateway to further collaboration between CNRS and MIT. The UMI, which is housed at MIT under the auspices of the MIT Energy Initiative (MITEI), has been designated by the CNRS as the lead unit of a “Laboratoire d’Excellence” consisting of multiple institutions engaged in materials science.