The Materials Science Division (MSD) research portfolio emphasizes defects and interfaces as a unifying theme for understanding condensed matter physics and materials science. This emphasis emerges from the hypothesis that exciting new science opportunities lie at the intersection of crystalline perfection with the natural or artificial heterogeneity of matter. As such, our research builds from the notion that the critical path to advancing the materials research frontier lies in understanding the structure, dynamics, and properties of defects and interfaces in bulk, thin film, and nanostructured forms, in some cases embracing the behavior induced by these defects. Making possible these studies are our well-established strengths in synthesis, world-leading expertise in coherent scattering by X-rays and electrons, and a growing emphasis across MSD on data science for materials. Looking forward, the advent of artificial intelligence, the rise of quantum information science and technology, the growth of microelectronics, and the importance of materials sustainability will all play key roles in how MSD research evolves into the future.