Unraveling Materials Synthesis Mechanisms Using In Situ Transmission Electron Microscopy and Neutron Scattering

Achieving precise control of materials synthesis is a cornerstone of modern manufacturing, driving efficiency, functionality, and device innovation. This review examines the roles of in situ transmission electron microscopy (TEM) and neutron scattering (NS) in advancing our understanding of these processes. In situ TEM offers atomic-scale insights into nucleation, growth, and phase transitions, while NS provides an analysis of reaction pathways, phase evolution, and structural transformations over broader length scales. Recent advancements in hardware have greatly improved spatial, temporal, and environmental control in in situ experiments. TEM enables breakthroughs in thermally controlled synthesis, gas-phase deposition, and beam-induced fabrication, including single-atom device creation. NS, particularly in situ neutron diffraction and imaging, are essential for studying bulk-level synthesis pathways. Together, these techniques offer a multiscale view of synthesis and processing. Integrating artificial intelligence (AI), automated workflows, and multimodal characterization is highlighted as a path toward high-throughput, predictive synthesis. By discussing challenges and opportunities in instrumentation and analysis, this review proposes a multiscale approach to accelerate innovation in materials synthesis, with applications across energy storage, quantum materials, and next-generation manufacturing.