The Zetasizer Nano series of instruments, in conjunction with appropriate accessories, allows for the measurement of surface zeta potential (i.e. the zeta potential of planar surfaces) and characterization of rheological properties of molecular solutions (i.e. DLS microrheology). Both of the measurement types require the use of tracer particles and selection of the most appropriate tracer is important in determining the success of the measurements. This technical note discusses the requirements of the tracers for use with surface zeta potential and microrheology measurements.