To meet national policy "to sustain a safe, secure, and effective U.S. nuclear stockpile as long as nuclear weapons exist," NNSA's Defense Programs need to make weapons. The challenge of being able to afford both the infrastructure and the production costs for lifetime extensions to the stockpile has created a mission need for flexible and reduced-cost product-based solutions to materials through accelerated qualification, certification and assessment. The science challenge to this need lies between the atomic scale of materials and the integral hydrodynamic-test scale, at the middle or "mesoscale" where interfaces, defects and microstructure determine the performance of the materials over the weapon’s lifecycle. Time-dependent control of the processing, structure and properties of materials at this scale lies at the heart of qualifying and certifying additive manufactured parts; high-fidelity and high-resolution experimental data at this scale are necessary to discover the right physical mechanisms to model and to validate and calibrate those reduced-order models in codes on exascale computers. The scientific requirements to do this are aided by a revolution in coherent imaging of non-periodic features that can be combined with scattering off periodic structures. This drives the mission need to require a coherent X-ray source, brilliant enough and with a high repetition rate of sufficiently high energy to see into and through the mesoscale. The Matter-Radiation Interactions in Extremes (MaRIE) Project is a proposal to build such a very-high-energy X-ray free electron laser uniquely matched to the NNSA mission. This effort is driving science and technology investment today "on the Roadmap to MaRIE," providing opportunities for early career scientists to engage in the central grand challenges of materials science.