Producing tunable material particles scalably and efficiently is desired for advancing medicine, energy storage, and conversion. The particle size distribution (PSD) impacts product performance and production efficiency, yet it is less understood and controlled compared to chemical composition due to production challenges in scalability and efficiency. This talk introduces an alternative low-cost process that scalably and directly precipitates uniform-size, composition-tunable particles or precursors in multiphase flow, enabling solid-state conversion with enhanced scalability and efficiency.