This book includes two parts: (I) spray pyrolysis for nanoparticles synthesis and (II) silicone-based MHz ultrasonic nozzles. The MHz ultrasonic nozzles aim at producing uniform precursor droplets of the sizes for the nanoparticles synthesis. Part (I) presents new findings on ultrasonic spray pyrolysis to produce nanoparticles of ZrO2. Part (II) presents the design, simulation, characterization and experimental results of micro-fabricated 0.5 MHz silicon-based ultrasonic nozzles. This book reports for the first time on successful ultrasonic atomization using micro-fabricated silicon Si-based high frequency ultrasonic nozzles of a novel design.