Traditional models of mineral formation through monomer-by-monomer addition have been challenged by recent evidence for crystallization through the addition of "particles," ranging from multi-ion complexes to fully formed nanocrystals. In many cases, organic adsorbates are thought to mediate the interaction between particles. Thus, in the case of soils, particle interactions should reflect their intimate relationship with the products of microbial activity and decay of plant matter. Because the distribution of elements within, the resulting mineral structures are expected to be radically different than that produced through traditional monomer-by-monomer growth, the resulting impact on soil chemistry and the outcome of microbial interactions should likewise be altered. However, much remains unknown about fundamental features of particle-based mineral growth, including the solution structure in the interfacial region between particles, the forces that drive assembly, and the relationships among solution structure, interfacial forces, and particle motion. The long-term vision of the proposed research is to develop a predictive understanding of particle-based growth that seamlessly crosses scales to connect molecular details to mesoscopic collective behavior. We will achieve this vision by obtaining quantitative data on structure, forces, and motion, and by developing the theoretical underpinnings to accurately describe the interaction and response of nanocrystals in electrolyte solutions. EMSL capabilities and expertise are essential to the success of the research. Particle interaction dynamics will be observed by in situ TEM. Structural and statistical analyses of particle attachment kinetics will utilize both in situ and cryogenic TEM (cryoTEM). Measurements of forces will be made by DFS and the structure of hydration layers will be probed via frequency modulated (FM) AFM and sum frequency surface spectroscopy (SFG). Fields, forces, and ion distributions at interfaces will be explored via atomistic simulations and DFT. This research will result in a methodology for connecting molecular details to mesoscopic collective behavior during particle-based crystal growth, as well as a body of knowledge that begins to fill the major gaps in our understanding of this growth mechanism.