Ultrasonic standing-wave atomization using two sonotrodes (20 kHz), both oscillating against each other, allows the disintegration of extremely viscous fluids (synthetic resins, highly concentrated suspensions) or fluids with high surface tension (metal melts) into narrow-sized, extremely small droplets and therefrom the production of fine spherical powders. The fundamentals of this new technique as well as its application in viscous fluid and melt atomization are described. Rapid solidification rates of metal powders (tin particles with mean diameters of less than 10 mu m) up to 2x10(-6) K/s for achieving ultra-fine cellular microstructures within the powder particles and, thus, for instance, supersaturation effects are further important advantages of this technique.