Metal nanoparticles (also known as colloidal metal) have been around for a very long time, with the original scientific references dating over one hundred and fifty years ago*. Both pure metal and metal oxide colloids are used in a wide variety of applications including catalysts, ferrofluids, biological markers, and many others. Particle size and zeta potential of these suspensions are critical physical parameters that affect functionality and stability. The SZ-100 Nanoparticle Analyzer is an excellent analytical tool for determining particle size and zeta potential of metal colloids.